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@@ -1,3521 +0,0 @@ -How fio works -------------- - -The first step in getting fio to simulate a desired I/O workload, is writing a -job file describing that specific setup. A job file may contain any number of -threads and/or files -- the typical contents of the job file is a *global* -section defining shared parameters, and one or more job sections describing the -jobs involved. When run, fio parses this file and sets everything up as -described. If we break down a job from top to bottom, it contains the following -basic parameters: - -`I/O type`_ - - Defines the I/O pattern issued to the file(s). We may only be reading - sequentially from this file(s), or we may be writing randomly. Or even - mixing reads and writes, sequentially or randomly. - Should we be doing buffered I/O, or direct/raw I/O? - -`Block size`_ - - In how large chunks are we issuing I/O? This may be a single value, - or it may describe a range of block sizes. - -`I/O size`_ - - How much data are we going to be reading/writing. - -`I/O engine`_ - - How do we issue I/O? We could be memory mapping the file, we could be - using regular read/write, we could be using splice, async I/O, or even - SG (SCSI generic sg). - -`I/O depth`_ - - If the I/O engine is async, how large a queuing depth do we want to - maintain? - - -`Target file/device`_ - - How many files are we spreading the workload over. - -`Threads, processes and job synchronization`_ - - How many threads or processes should we spread this workload over. - -The above are the basic parameters defined for a workload, in addition there's a -multitude of parameters that modify other aspects of how this job behaves. - - -Command line options --------------------- - -.. option:: --debug=type - - Enable verbose tracing of various fio actions. May be ``all`` for all types - or individual types separated by a comma (e.g. ``--debug=file,mem`` will - enable file and memory debugging). Currently, additional logging is - available for: - - *process* - Dump info related to processes. - *file* - Dump info related to file actions. - *io* - Dump info related to I/O queuing. - *mem* - Dump info related to memory allocations. - *blktrace* - Dump info related to blktrace setup. - *verify* - Dump info related to I/O verification. - *all* - Enable all debug options. - *random* - Dump info related to random offset generation. - *parse* - Dump info related to option matching and parsing. - *diskutil* - Dump info related to disk utilization updates. - *job:x* - Dump info only related to job number x. - *mutex* - Dump info only related to mutex up/down ops. - *profile* - Dump info related to profile extensions. - *time* - Dump info related to internal time keeping. - *net* - Dump info related to networking connections. - *rate* - Dump info related to I/O rate switching. - *compress* - Dump info related to log compress/decompress. - *?* or *help* - Show available debug options. - -.. option:: --parse-only - - Parse options only, don\'t start any I/O. - -.. option:: --output=filename - - Write output to file `filename`. - -.. option:: --bandwidth-log - - Generate aggregate bandwidth logs. - -.. option:: --minimal - - Print statistics in a terse, semicolon-delimited format. - -.. option:: --append-terse - - Print statistics in selected mode AND terse, semicolon-delimited format. - **deprecated**, use :option:`--output-format` instead to select multiple - formats. - -.. option:: --output-format=type - - Set the reporting format to `normal`, `terse`, `json`, or `json+`. Multiple - formats can be selected, separate by a comma. `terse` is a CSV based - format. `json+` is like `json`, except it adds a full dump of the latency - buckets. - -.. option:: --terse-version=type - - Set terse version output format (default 3, or 2 or 4). - -.. option:: --version - - Print version info and exit. - -.. option:: --help - - Print this page. - -.. option:: --cpuclock-test - - Perform test and validation of internal CPU clock. - -.. option:: --crctest=test - - Test the speed of the builtin checksumming functions. If no argument is - given, all of them are tested. Or a comma separated list can be passed, in - which case the given ones are tested. - -.. option:: --cmdhelp=command - - Print help information for `command`. May be ``all`` for all commands. - -.. option:: --enghelp=[ioengine[,command]] - - List all commands defined by :option:`ioengine`, or print help for `command` - defined by :option:`ioengine`. If no :option:`ioengine` is given, list all - available ioengines. - -.. option:: --showcmd=jobfile - - Turn a job file into command line options. - -.. option:: --readonly - - Turn on safety read-only checks, preventing writes. The ``--readonly`` - option is an extra safety guard to prevent users from accidentally starting - a write workload when that is not desired. Fio will only write if - `rw=write/randwrite/rw/randrw` is given. This extra safety net can be used - as an extra precaution as ``--readonly`` will also enable a write check in - the I/O engine core to prevent writes due to unknown user space bug(s). - -.. option:: --eta=when - - When real-time ETA estimate should be printed. May be `always`, `never` or - `auto`. - -.. option:: --eta-newline=time - - Force a new line for every `time` period passed. - -.. option:: --status-interval=time - - Force full status dump every `time` period passed. - -.. option:: --section=name - - Only run specified section in job file. Multiple sections can be specified. - The ``--section`` option allows one to combine related jobs into one file. - E.g. one job file could define light, moderate, and heavy sections. Tell - fio to run only the "heavy" section by giving ``--section=heavy`` - command line option. One can also specify the "write" operations in one - section and "verify" operation in another section. The ``--section`` option - only applies to job sections. The reserved *global* section is always - parsed and used. - -.. option:: --alloc-size=kb - - Set the internal smalloc pool to this size in kb (def 1024). The - ``--alloc-size`` switch allows one to use a larger pool size for smalloc. - If running large jobs with randommap enabled, fio can run out of memory. - Smalloc is an internal allocator for shared structures from a fixed size - memory pool. The pool size defaults to 16M and can grow to 8 pools. - - NOTE: While running :file:`.fio_smalloc.*` backing store files are visible - in :file:`/tmp`. - -.. option:: --warnings-fatal - - All fio parser warnings are fatal, causing fio to exit with an - error. - -.. option:: --max-jobs=nr - - Maximum number of threads/processes to support. - -.. option:: --server=args - - Start a backend server, with `args` specifying what to listen to. - See `Client/Server`_ section. - -.. option:: --daemonize=pidfile - - Background a fio server, writing the pid to the given `pidfile` file. - -.. option:: --client=hostname - - Instead of running the jobs locally, send and run them on the given host or - set of hosts. See `Client/Server`_ section. - -.. option:: --remote-config=file - - Tell fio server to load this local file. - -.. option:: --idle-prof=option - - Report cpu idleness on a system or percpu basis - ``--idle-prof=system,percpu`` or - run unit work calibration only ``--idle-prof=calibrate``. - -.. option:: --inflate-log=log - - Inflate and output compressed log. - -.. option:: --trigger-file=file - - Execute trigger cmd when file exists. - -.. option:: --trigger-timeout=t - - Execute trigger at this time. - -.. option:: --trigger=cmd - - Set this command as local trigger. - -.. option:: --trigger-remote=cmd - - Set this command as remote trigger. - -.. option:: --aux-path=path - - Use this path for fio state generated files. - -Any parameters following the options will be assumed to be job files, unless -they match a job file parameter. Multiple job files can be listed and each job -file will be regarded as a separate group. Fio will :option:`stonewall` -execution between each group. - - -Job file format ---------------- - -As previously described, fio accepts one or more job files describing what it is -supposed to do. The job file format is the classic ini file, where the names -enclosed in [] brackets define the job name. You are free to use any ASCII name -you want, except *global* which has special meaning. Following the job name is -a sequence of zero or more parameters, one per line, that define the behavior of -the job. If the first character in a line is a ';' or a '#', the entire line is -discarded as a comment. - -A *global* section sets defaults for the jobs described in that file. A job may -override a *global* section parameter, and a job file may even have several -*global* sections if so desired. A job is only affected by a *global* section -residing above it. - -The :option:`--cmdhelp` option also lists all options. If used with an `option` -argument, :option:`--cmdhelp` will detail the given `option`. - -See the `examples/` directory for inspiration on how to write job files. Note -the copyright and license requirements currently apply to `examples/` files. - -So let's look at a really simple job file that defines two processes, each -randomly reading from a 128MiB file: - -.. code-block:: ini - - ; -- start job file -- - [global] - rw=randread - size=128m - - [job1] - - [job2] - - ; -- end job file -- - -As you can see, the job file sections themselves are empty as all the described -parameters are shared. As no :option:`filename` option is given, fio makes up a -`filename` for each of the jobs as it sees fit. On the command line, this job -would look as follows:: - -$ fio --name=global --rw=randread --size=128m --name=job1 --name=job2 - - -Let's look at an example that has a number of processes writing randomly to -files: - -.. code-block:: ini - - ; -- start job file -- - [random-writers] - ioengine=libaio - iodepth=4 - rw=randwrite - bs=32k - direct=0 - size=64m - numjobs=4 - ; -- end job file -- - -Here we have no *global* section, as we only have one job defined anyway. We -want to use async I/O here, with a depth of 4 for each file. We also increased -the buffer size used to 32KiB and define numjobs to 4 to fork 4 identical -jobs. The result is 4 processes each randomly writing to their own 64MiB -file. Instead of using the above job file, you could have given the parameters -on the command line. For this case, you would specify:: - -$ fio --name=random-writers --ioengine=libaio --iodepth=4 --rw=randwrite --bs=32k --direct=0 --size=64m --numjobs=4 - -When fio is utilized as a basis of any reasonably large test suite, it might be -desirable to share a set of standardized settings across multiple job files. -Instead of copy/pasting such settings, any section may pull in an external -:file:`filename.fio` file with *include filename* directive, as in the following -example:: - - ; -- start job file including.fio -- - [global] - filename=/tmp/test - filesize=1m - include glob-include.fio - - [test] - rw=randread - bs=4k - time_based=1 - runtime=10 - include test-include.fio - ; -- end job file including.fio -- - -.. code-block:: ini - - ; -- start job file glob-include.fio -- - thread=1 - group_reporting=1 - ; -- end job file glob-include.fio -- - -.. code-block:: ini - - ; -- start job file test-include.fio -- - ioengine=libaio - iodepth=4 - ; -- end job file test-include.fio -- - -Settings pulled into a section apply to that section only (except *global* -section). Include directives may be nested in that any included file may contain -further include directive(s). Include files may not contain [] sections. - - -Environment variables -~~~~~~~~~~~~~~~~~~~~~ - -Fio also supports environment variable expansion in job files. Any sub-string of -the form ``${VARNAME}`` as part of an option value (in other words, on the right -of the '='), will be expanded to the value of the environment variable called -`VARNAME`. If no such environment variable is defined, or `VARNAME` is the -empty string, the empty string will be substituted. - -As an example, let's look at a sample fio invocation and job file:: - -$ SIZE=64m NUMJOBS=4 fio jobfile.fio - -.. code-block:: ini - - ; -- start job file -- - [random-writers] - rw=randwrite - size=${SIZE} - numjobs=${NUMJOBS} - ; -- end job file -- - -This will expand to the following equivalent job file at runtime: - -.. code-block:: ini - - ; -- start job file -- - [random-writers] - rw=randwrite - size=64m - numjobs=4 - ; -- end job file -- - -Fio ships with a few example job files, you can also look there for inspiration. - -Reserved keywords -~~~~~~~~~~~~~~~~~ - -Additionally, fio has a set of reserved keywords that will be replaced -internally with the appropriate value. Those keywords are: - -**$pagesize** - - The architecture page size of the running system. - -**$mb_memory** - - Megabytes of total memory in the system. - -**$ncpus** - - Number of online available CPUs. - -These can be used on the command line or in the job file, and will be -automatically substituted with the current system values when the job is -run. Simple math is also supported on these keywords, so you can perform actions -like:: - - size=8*$mb_memory - -and get that properly expanded to 8 times the size of memory in the machine. - - -Job file parameters -------------------- - -This section describes in details each parameter associated with a job. Some -parameters take an option of a given type, such as an integer or a -string. Anywhere a numeric value is required, an arithmetic expression may be -used, provided it is surrounded by parentheses. Supported operators are: - - - addition (+) - - subtraction (-) - - multiplication (*) - - division (/) - - modulus (%) - - exponentiation (^) - -For time values in expressions, units are microseconds by default. This is -different than for time values not in expressions (not enclosed in -parentheses). The following types are used: - - -Parameter types -~~~~~~~~~~~~~~~ - -**str** - String. This is a sequence of alpha characters. - -**time** - Integer with possible time suffix. In seconds unless otherwise - specified, use e.g. 10m for 10 minutes. Accepts s/m/h for seconds, minutes, - and hours, and accepts 'ms' (or 'msec') for milliseconds, and 'us' (or - 'usec') for microseconds. - -.. _int: - -**int** - Integer. A whole number value, which may contain an integer prefix - and an integer suffix: - - [*integer prefix*] **number** [*integer suffix*] - - The optional *integer prefix* specifies the number's base. The default - is decimal. *0x* specifies hexadecimal. - - The optional *integer suffix* specifies the number's units, and includes an - optional unit prefix and an optional unit. For quantities of data, the - default unit is bytes. For quantities of time, the default unit is seconds. - - With :option:`kb_base` =1000, fio follows international standards for unit - prefixes. To specify power-of-10 decimal values defined in the - International System of Units (SI): - - * *Ki* -- means kilo (K) or 1000 - * *Mi* -- means mega (M) or 1000**2 - * *Gi* -- means giga (G) or 1000**3 - * *Ti* -- means tera (T) or 1000**4 - * *Pi* -- means peta (P) or 1000**5 - - To specify power-of-2 binary values defined in IEC 80000-13: - - * *k* -- means kibi (Ki) or 1024 - * *M* -- means mebi (Mi) or 1024**2 - * *G* -- means gibi (Gi) or 1024**3 - * *T* -- means tebi (Ti) or 1024**4 - * *P* -- means pebi (Pi) or 1024**5 - - With :option:`kb_base` =1024 (the default), the unit prefixes are opposite - from those specified in the SI and IEC 80000-13 standards to provide - compatibility with old scripts. For example, 4k means 4096. - - For quantities of data, an optional unit of 'B' may be included - (e.g., 'kB' is the same as 'k'). - - The *integer suffix* is not case sensitive (e.g., m/mi mean mebi/mega, - not milli). 'b' and 'B' both mean byte, not bit. - - Examples with :option:`kb_base` =1000: - - * *4 KiB*: 4096, 4096b, 4096B, 4ki, 4kib, 4kiB, 4Ki, 4KiB - * *1 MiB*: 1048576, 1mi, 1024ki - * *1 MB*: 1000000, 1m, 1000k - * *1 TiB*: 1099511627776, 1ti, 1024gi, 1048576mi - * *1 TB*: 1000000000, 1t, 1000m, 1000000k - - Examples with :option:`kb_base` =1024 (default): - - * *4 KiB*: 4096, 4096b, 4096B, 4k, 4kb, 4kB, 4K, 4KB - * *1 MiB*: 1048576, 1m, 1024k - * *1 MB*: 1000000, 1mi, 1000ki - * *1 TiB*: 1099511627776, 1t, 1024g, 1048576m - * *1 TB*: 1000000000, 1ti, 1000mi, 1000000ki - - To specify times (units are not case sensitive): - - * *D* -- means days - * *H* -- means hours - * *M* -- mean minutes - * *s* -- or sec means seconds (default) - * *ms* -- or *msec* means milliseconds - * *us* -- or *usec* means microseconds - - If the option accepts an upper and lower range, use a colon ':' or - minus '-' to separate such values. See :ref:`irange <irange>`. - If the lower value specified happens to be larger than the upper value, - two values are swapped. - -.. _bool: - -**bool** - Boolean. Usually parsed as an integer, however only defined for - true and false (1 and 0). - -.. _irange: - -**irange** - Integer range with suffix. Allows value range to be given, such as - 1024-4096. A colon may also be used as the separator, e.g. 1k:4k. If the - option allows two sets of ranges, they can be specified with a ',' or '/' - delimiter: 1k-4k/8k-32k. Also see :ref:`int <int>`. - -**float_list** - A list of floating point numbers, separated by a ':' character. - - -Units -~~~~~ - -.. option:: kb_base=int - - Select the interpretation of unit prefixes in input parameters. - - **1000** - Inputs comply with IEC 80000-13 and the International - System of Units (SI). Use: - - - power-of-2 values with IEC prefixes (e.g., KiB) - - power-of-10 values with SI prefixes (e.g., kB) - - **1024** - Compatibility mode (default). To avoid breaking old scripts: - - - power-of-2 values with SI prefixes - - power-of-10 values with IEC prefixes - - See :option:`bs` for more details on input parameters. - - Outputs always use correct prefixes. Most outputs include both - side-by-side, like:: - - bw=2383.3kB/s (2327.4KiB/s) - - If only one value is reported, then kb_base selects the one to use: - - **1000** -- SI prefixes - - **1024** -- IEC prefixes - -.. option:: unit_base=int - - Base unit for reporting. Allowed values are: - - **0** - Use auto-detection (default). - **8** - Byte based. - **1** - Bit based. - - -With the above in mind, here follows the complete list of fio job parameters. - - -Job description -~~~~~~~~~~~~~~~ - -.. option:: name=str - - ASCII name of the job. This may be used to override the name printed by fio - for this job. Otherwise the job name is used. On the command line this - parameter has the special purpose of also signaling the start of a new job. - -.. option:: description=str - - Text description of the job. Doesn't do anything except dump this text - description when this job is run. It's not parsed. - -.. option:: loops=int - - Run the specified number of iterations of this job. Used to repeat the same - workload a given number of times. Defaults to 1. - -.. option:: numjobs=int - - Create the specified number of clones of this job. Each clone of job - is spawned as an independent thread or process. May be used to setup a - larger number of threads/processes doing the same thing. Each thread is - reported separately; to see statistics for all clones as a whole, use - :option:`group_reporting` in conjunction with :option:`new_group`. - See :option:`--max-jobs`. - - -Time related parameters -~~~~~~~~~~~~~~~~~~~~~~~ - -.. option:: runtime=time - - Tell fio to terminate processing after the specified period of time. It - can be quite hard to determine for how long a specified job will run, so - this parameter is handy to cap the total runtime to a given time. When - the unit is omitted, the value is given in seconds. - -.. option:: time_based - - If set, fio will run for the duration of the :option:`runtime` specified - even if the file(s) are completely read or written. It will simply loop over - the same workload as many times as the :option:`runtime` allows. - -.. option:: startdelay=irange(time) - - Delay start of job for the specified number of seconds. Supports all time - suffixes to allow specification of hours, minutes, seconds and milliseconds - -- seconds are the default if a unit is omitted. Can be given as a range - which causes each thread to choose randomly out of the range. - -.. option:: ramp_time=time - - If set, fio will run the specified workload for this amount of time before - logging any performance numbers. Useful for letting performance settle - before logging results, thus minimizing the runtime required for stable - results. Note that the ``ramp_time`` is considered lead in time for a job, - thus it will increase the total runtime if a special timeout or - :option:`runtime` is specified. When the unit is omitted, the value is - given in seconds. - -.. option:: clocksource=str - - Use the given clocksource as the base of timing. The supported options are: - - **gettimeofday** - :manpage:`gettimeofday(2)` - - **clock_gettime** - :manpage:`clock_gettime(2)` - - **cpu** - Internal CPU clock source - - cpu is the preferred clocksource if it is reliable, as it is very fast (and - fio is heavy on time calls). Fio will automatically use this clocksource if - it's supported and considered reliable on the system it is running on, - unless another clocksource is specifically set. For x86/x86-64 CPUs, this - means supporting TSC Invariant. - -.. option:: gtod_reduce=bool - - Enable all of the :manpage:`gettimeofday(2)` reducing options - (:option:`disable_clat`, :option:`disable_slat`, :option:`disable_bw_measurement`) plus - reduce precision of the timeout somewhat to really shrink the - :manpage:`gettimeofday(2)` call count. With this option enabled, we only do - about 0.4% of the :manpage:`gettimeofday(2)` calls we would have done if all - time keeping was enabled. - -.. option:: gtod_cpu=int - - Sometimes it's cheaper to dedicate a single thread of execution to just - getting the current time. Fio (and databases, for instance) are very - intensive on :manpage:`gettimeofday(2)` calls. With this option, you can set - one CPU aside for doing nothing but logging current time to a shared memory - location. Then the other threads/processes that run I/O workloads need only - copy that segment, instead of entering the kernel with a - :manpage:`gettimeofday(2)` call. The CPU set aside for doing these time - calls will be excluded from other uses. Fio will manually clear it from the - CPU mask of other jobs. - - -Target file/device -~~~~~~~~~~~~~~~~~~ - -.. option:: directory=str - - Prefix filenames with this directory. Used to place files in a different - location than :file:`./`. You can specify a number of directories by - separating the names with a ':' character. These directories will be - assigned equally distributed to job clones creates with :option:`numjobs` as - long as they are using generated filenames. If specific `filename(s)` are - set fio will use the first listed directory, and thereby matching the - `filename` semantic which generates a file each clone if not specified, but - let all clones use the same if set. - - See the :option:`filename` option for escaping certain characters. - -.. option:: filename=str - - Fio normally makes up a `filename` based on the job name, thread number, and - file number. If you want to share files between threads in a job or several - jobs with fixed file paths, specify a `filename` for each of them to override - the default. If the ioengine is file based, you can specify a number of files - by separating the names with a ':' colon. So if you wanted a job to open - :file:`/dev/sda` and :file:`/dev/sdb` as the two working files, you would use - ``filename=/dev/sda:/dev/sdb``. This also means that whenever this option is - specified, :option:`nrfiles` is ignored. The size of regular files specified - by this option will be :option:`size` divided by number of files unless - explicit size is specified by :option:`filesize`. - - On Windows, disk devices are accessed as :file:`\\\\.\\PhysicalDrive0` for - the first device, :file:`\\\\.\\PhysicalDrive1` for the second etc. - Note: Windows and FreeBSD prevent write access to areas - of the disk containing in-use data (e.g. filesystems). If the wanted - `filename` does need to include a colon, then escape that with a ``\`` - character. For instance, if the `filename` is :file:`/dev/dsk/foo@3,0:c`, - then you would use ``filename="/dev/dsk/foo@3,0\:c"``. The - :file:`-` is a reserved name, meaning stdin or stdout. Which of the two - depends on the read/write direction set. - -.. option:: filename_format=str - - If sharing multiple files between jobs, it is usually necessary to have fio - generate the exact names that you want. By default, fio will name a file - based on the default file format specification of - :file:`jobname.jobnumber.filenumber`. With this option, that can be - customized. Fio will recognize and replace the following keywords in this - string: - - **$jobname** - The name of the worker thread or process. - **$jobnum** - The incremental number of the worker thread or process. - **$filenum** - The incremental number of the file for that worker thread or - process. - - To have dependent jobs share a set of files, this option can be set to have - fio generate filenames that are shared between the two. For instance, if - :file:`testfiles.$filenum` is specified, file number 4 for any job will be - named :file:`testfiles.4`. The default of :file:`$jobname.$jobnum.$filenum` - will be used if no other format specifier is given. - -.. option:: unique_filename=bool - - To avoid collisions between networked clients, fio defaults to prefixing any - generated filenames (with a directory specified) with the source of the - client connecting. To disable this behavior, set this option to 0. - -.. option:: opendir=str - - Recursively open any files below directory `str`. - -.. option:: lockfile=str - - Fio defaults to not locking any files before it does I/O to them. If a file - or file descriptor is shared, fio can serialize I/O to that file to make the - end result consistent. This is usual for emulating real workloads that share - files. The lock modes are: - - **none** - No locking. The default. - **exclusive** - Only one thread or process may do I/O at a time, excluding all - others. - **readwrite** - Read-write locking on the file. Many readers may - access the file at the same time, but writes get exclusive access. - -.. option:: nrfiles=int - - Number of files to use for this job. Defaults to 1. The size of files - will be :option:`size` divided by this unless explicit size is specified by - :option:`filesize`. Files are created for each thread separately, and each - file will have a file number within its name by default, as explained in - :option:`filename` section. - - -.. option:: openfiles=int - - Number of files to keep open at the same time. Defaults to the same as - :option:`nrfiles`, can be set smaller to limit the number simultaneous - opens. - -.. option:: file_service_type=str - - Defines how fio decides which file from a job to service next. The following - types are defined: - - **random** - Choose a file at random. - - **roundrobin** - Round robin over opened files. This is the default. - - **sequential** - Finish one file before moving on to the next. Multiple files can - still be open depending on 'openfiles'. - - **zipf** - Use a *Zipf* distribution to decide what file to access. - - **pareto** - Use a *Pareto* distribution to decide what file to access. - - **gauss** - Use a *Gaussian* (normal) distribution to decide what file to - access. - - For *random*, *roundrobin*, and *sequential*, a postfix can be appended to - tell fio how many I/Os to issue before switching to a new file. For example, - specifying ``file_service_type=random:8`` would cause fio to issue - 8 I/Os before selecting a new file at random. For the non-uniform - distributions, a floating point postfix can be given to influence how the - distribution is skewed. See :option:`random_distribution` for a description - of how that would work. - -.. option:: ioscheduler=str - - Attempt to switch the device hosting the file to the specified I/O scheduler - before running. - -.. option:: create_serialize=bool - - If true, serialize the file creation for the jobs. This may be handy to - avoid interleaving of data files, which may greatly depend on the filesystem - used and even the number of processors in the system. - -.. option:: create_fsync=bool - - fsync the data file after creation. This is the default. - -.. option:: create_on_open=bool - - Don't pre-setup the files for I/O, just create open() when it's time to do - I/O to that file. - -.. option:: create_only=bool - - If true, fio will only run the setup phase of the job. If files need to be - laid out or updated on disk, only that will be done. The actual job contents - are not executed. - -.. option:: allow_file_create=bool - - If true, fio is permitted to create files as part of its workload. This is - the default behavior. If this option is false, then fio will error out if - the files it needs to use don't already exist. Default: true. - -.. option:: allow_mounted_write=bool - - If this isn't set, fio will abort jobs that are destructive (e.g. that write) - to what appears to be a mounted device or partition. This should help catch - creating inadvertently destructive tests, not realizing that the test will - destroy data on the mounted file system. Note that some platforms don't allow - writing against a mounted device regardless of this option. Default: false. - -.. option:: pre_read=bool - - If this is given, files will be pre-read into memory before starting the - given I/O operation. This will also clear the :option:`invalidate` flag, - since it is pointless to pre-read and then drop the cache. This will only - work for I/O engines that are seek-able, since they allow you to read the - same data multiple times. Thus it will not work on e.g. network or splice I/O. - -.. option:: unlink=bool - - Unlink the job files when done. Not the default, as repeated runs of that - job would then waste time recreating the file set again and again. - -.. option:: unlink_each_loop=bool - - Unlink job files after each iteration or loop. - -.. option:: zonesize=int - - Divide a file into zones of the specified size. See :option:`zoneskip`. - -.. option:: zonerange=int - - Give size of an I/O zone. See :option:`zoneskip`. - -.. option:: zoneskip=int - - Skip the specified number of bytes when :option:`zonesize` data has been - read. The two zone options can be used to only do I/O on zones of a file. - - -I/O type -~~~~~~~~ - -.. option:: direct=bool - - If value is true, use non-buffered I/O. This is usually O_DIRECT. Note that - ZFS on Solaris doesn't support direct I/O. On Windows the synchronous - ioengines don't support direct I/O. Default: false. - -.. option:: atomic=bool - - If value is true, attempt to use atomic direct I/O. Atomic writes are - guaranteed to be stable once acknowledged by the operating system. Only - Linux supports O_ATOMIC right now. - -.. option:: buffered=bool - - If value is true, use buffered I/O. This is the opposite of the - :option:`direct` option. Defaults to true. - -.. option:: readwrite=str, rw=str - - Type of I/O pattern. Accepted values are: - - **read** - Sequential reads. - **write** - Sequential writes. - **trim** - Sequential trims (Linux block devices only). - **randwrite** - Random writes. - **randread** - Random reads. - **randtrim** - Random trims (Linux block devices only). - **rw,readwrite** - Sequential mixed reads and writes. - **randrw** - Random mixed reads and writes. - **trimwrite** - Sequential trim+write sequences. Blocks will be trimmed first, - then the same blocks will be written to. - - Fio defaults to read if the option is not specified. For the mixed I/O - types, the default is to split them 50/50. For certain types of I/O the - result may still be skewed a bit, since the speed may be different. It is - possible to specify a number of I/O's to do before getting a new offset, - this is done by appending a ``:<nr>`` to the end of the string given. For a - random read, it would look like ``rw=randread:8`` for passing in an offset - modifier with a value of 8. If the suffix is used with a sequential I/O - pattern, then the value specified will be added to the generated offset for - each I/O. For instance, using ``rw=write:4k`` will skip 4k for every - write. It turns sequential I/O into sequential I/O with holes. See the - :option:`rw_sequencer` option. - -.. option:: rw_sequencer=str - - If an offset modifier is given by appending a number to the ``rw=<str>`` - line, then this option controls how that number modifies the I/O offset - being generated. Accepted values are: - - **sequential** - Generate sequential offset. - **identical** - Generate the same offset. - - ``sequential`` is only useful for random I/O, where fio would normally - generate a new random offset for every I/O. If you append e.g. 8 to randread, - you would get a new random offset for every 8 I/O's. The result would be a - seek for only every 8 I/O's, instead of for every I/O. Use ``rw=randread:8`` - to specify that. As sequential I/O is already sequential, setting - ``sequential`` for that would not result in any differences. ``identical`` - behaves in a similar fashion, except it sends the same offset 8 number of - times before generating a new offset. - -.. option:: unified_rw_reporting=bool - - Fio normally reports statistics on a per data direction basis, meaning that - reads, writes, and trims are accounted and reported separately. If this - option is set fio sums the results and report them as "mixed" instead. - -.. option:: randrepeat=bool - - Seed the random number generator used for random I/O patterns in a - predictable way so the pattern is repeatable across runs. Default: true. - -.. option:: allrandrepeat=bool - - Seed all random number generators in a predictable way so results are - repeatable across runs. Default: false. - -.. option:: randseed=int - - Seed the random number generators based on this seed value, to be able to - control what sequence of output is being generated. If not set, the random - sequence depends on the :option:`randrepeat` setting. - -.. option:: fallocate=str - - Whether pre-allocation is performed when laying down files. - Accepted values are: - - **none** - Do not pre-allocate space. - - **posix** - Pre-allocate via :manpage:`posix_fallocate(3)`. - - **keep** - Pre-allocate via :manpage:`fallocate(2)` with - FALLOC_FL_KEEP_SIZE set. - - **0** - Backward-compatible alias for **none**. - - **1** - Backward-compatible alias for **posix**. - - May not be available on all supported platforms. **keep** is only available - on Linux. If using ZFS on Solaris this must be set to **none** because ZFS - doesn't support it. Default: **posix**. - -.. option:: fadvise_hint=str - - Use :manpage:`posix_fadvise(2)` to advise the kernel on what I/O patterns - are likely to be issued. Accepted values are: - - **0** - Backwards-compatible hint for "no hint". - - **1** - Backwards compatible hint for "advise with fio workload type". This - uses **FADV_RANDOM** for a random workload, and **FADV_SEQUENTIAL** - for a sequential workload. - - **sequential** - Advise using **FADV_SEQUENTIAL**. - - **random** - Advise using **FADV_RANDOM**. - -.. option:: fadvise_stream=int - - Use :manpage:`posix_fadvise(2)` to advise the kernel what stream ID the - writes issued belong to. Only supported on Linux. Note, this option may - change going forward. - -.. option:: offset=int - - Start I/O at the given offset in the file. The data before the given offset - will not be touched. This effectively caps the file size at `real_size - - offset`. Can be combined with :option:`size` to constrain the start and - end range that I/O will be done within. - -.. option:: offset_increment=int - - If this is provided, then the real offset becomes `offset + offset_increment - * thread_number`, where the thread number is a counter that starts at 0 and - is incremented for each sub-job (i.e. when :option:`numjobs` option is - specified). This option is useful if there are several jobs which are - intended to operate on a file in parallel disjoint segments, with even - spacing between the starting points. - -.. option:: number_ios=int - - Fio will normally perform I/Os until it has exhausted the size of the region - set by :option:`size`, or if it exhaust the allocated time (or hits an error - condition). With this setting, the range/size can be set independently of - the number of I/Os to perform. When fio reaches this number, it will exit - normally and report status. Note that this does not extend the amount of I/O - that will be done, it will only stop fio if this condition is met before - other end-of-job criteria. - -.. option:: fsync=int - - If writing to a file, issue a sync of the dirty data for every number of - blocks given. For example, if you give 32 as a parameter, fio will sync the - file for every 32 writes issued. If fio is using non-buffered I/O, we may - not sync the file. The exception is the sg I/O engine, which synchronizes - the disk cache anyway. Defaults to 0, which means no sync every certain - number of writes. - -.. option:: fdatasync=int - - Like :option:`fsync` but uses :manpage:`fdatasync(2)` to only sync data and - not metadata blocks. In Windows, FreeBSD, and DragonFlyBSD there is no - :manpage:`fdatasync(2)`, this falls back to using :manpage:`fsync(2)`. - Defaults to 0, which means no sync data every certain number of writes. - -.. option:: write_barrier=int - - Make every `N-th` write a barrier write. - -.. option:: sync_file_range=str:val - - Use :manpage:`sync_file_range(2)` for every `val` number of write - operations. Fio will track range of writes that have happened since the last - :manpage:`sync_file_range(2)` call. `str` can currently be one or more of: - - **wait_before** - SYNC_FILE_RANGE_WAIT_BEFORE - **write** - SYNC_FILE_RANGE_WRITE - **wait_after** - SYNC_FILE_RANGE_WAIT_AFTER - - So if you do ``sync_file_range=wait_before,write:8``, fio would use - ``SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE`` for every 8 - writes. Also see the :manpage:`sync_file_range(2)` man page. This option is - Linux specific. - -.. option:: overwrite=bool - - If true, writes to a file will always overwrite existing data. If the file - doesn't already exist, it will be created before the write phase begins. If - the file exists and is large enough for the specified write phase, nothing - will be done. - -.. option:: end_fsync=bool - - If true, fsync file contents when a write stage has completed. - -.. option:: fsync_on_close=bool - - If true, fio will :manpage:`fsync(2)` a dirty file on close. This differs - from end_fsync in that it will happen on every file close, not just at the - end of the job. - -.. option:: rwmixread=int - - Percentage of a mixed workload that should be reads. Default: 50. - -.. option:: rwmixwrite=int - - Percentage of a mixed workload that should be writes. If both - :option:`rwmixread` and :option:`rwmixwrite` is given and the values do not - add up to 100%, the latter of the two will be used to override the - first. This may interfere with a given rate setting, if fio is asked to - limit reads or writes to a certain rate. If that is the case, then the - distribution may be skewed. Default: 50. - -.. option:: random_distribution=str:float[,str:float][,str:float] - - By default, fio will use a completely uniform random distribution when asked - to perform random I/O. Sometimes it is useful to skew the distribution in - specific ways, ensuring that some parts of the data is more hot than others. - fio includes the following distribution models: - - **random** - Uniform random distribution - - **zipf** - Zipf distribution - - **pareto** - Pareto distribution - - **gauss** - Normal (Gaussian) distribution - - **zoned** - Zoned random distribution - - When using a **zipf** or **pareto** distribution, an input value is also - needed to define the access pattern. For **zipf**, this is the `zipf - theta`. For **pareto**, it's the `Pareto power`. Fio includes a test - program, :command:`genzipf`, that can be used visualize what the given input - values will yield in terms of hit rates. If you wanted to use **zipf** with - a `theta` of 1.2, you would use ``random_distribution=zipf:1.2`` as the - option. If a non-uniform model is used, fio will disable use of the random - map. For the **gauss** distribution, a normal deviation is supplied as a - value between 0 and 100. - - For a **zoned** distribution, fio supports specifying percentages of I/O - access that should fall within what range of the file or device. For - example, given a criteria of: - - * 60% of accesses should be to the first 10% - * 30% of accesses should be to the next 20% - * 8% of accesses should be to to the next 30% - * 2% of accesses should be to the next 40% - - we can define that through zoning of the random accesses. For the above - example, the user would do:: - - random_distribution=zoned:60/10:30/20:8/30:2/40 - - similarly to how :option:`bssplit` works for setting ranges and percentages - of block sizes. Like :option:`bssplit`, it's possible to specify separate - zones for reads, writes, and trims. If just one set is given, it'll apply to - all of them. - -.. option:: percentage_random=int[,int][,int] - - For a random workload, set how big a percentage should be random. This - defaults to 100%, in which case the workload is fully random. It can be set - from anywhere from 0 to 100. Setting it to 0 would make the workload fully - sequential. Any setting in between will result in a random mix of sequential - and random I/O, at the given percentages. Comma-separated values may be - specified for reads, writes, and trims as described in :option:`blocksize`. - -.. option:: norandommap - - Normally fio will cover every block of the file when doing random I/O. If - this option is given, fio will just get a new random offset without looking - at past I/O history. This means that some blocks may not be read or written, - and that some blocks may be read/written more than once. If this option is - used with :option:`verify` and multiple blocksizes (via :option:`bsrange`), - only intact blocks are verified, i.e., partially-overwritten blocks are - ignored. - -.. option:: softrandommap=bool - - See :option:`norandommap`. If fio runs with the random block map enabled and - it fails to allocate the map, if this option is set it will continue without - a random block map. As coverage will not be as complete as with random maps, - this option is disabled by default. - -.. option:: random_generator=str - - Fio supports the following engines for generating - I/O offsets for random I/O: - - **tausworthe** - Strong 2^88 cycle random number generator - **lfsr** - Linear feedback shift register generator - **tausworthe64** - Strong 64-bit 2^258 cycle random number generator - - **tausworthe** is a strong random number generator, but it requires tracking - on the side if we want to ensure that blocks are only read or written - once. **LFSR** guarantees that we never generate the same offset twice, and - it's also less computationally expensive. It's not a true random generator, - however, though for I/O purposes it's typically good enough. **LFSR** only - works with single block sizes, not with workloads that use multiple block - sizes. If used with such a workload, fio may read or write some blocks - multiple times. The default value is **tausworthe**, unless the required - space exceeds 2^32 blocks. If it does, then **tausworthe64** is - selected automatically. - - -Block size -~~~~~~~~~~ - -.. option:: blocksize=int[,int][,int], bs=int[,int][,int] - - The block size in bytes used for I/O units. Default: 4096. A single value - applies to reads, writes, and trims. Comma-separated values may be - specified for reads, writes, and trims. A value not terminated in a comma - applies to subsequent types. - - Examples: - - **bs=256k** - means 256k for reads, writes and trims. - - **bs=8k,32k** - means 8k for reads, 32k for writes and trims. - - **bs=8k,32k,** - means 8k for reads, 32k for writes, and default for trims. - - **bs=,8k** - means default for reads, 8k for writes and trims. - - **bs=,8k,** - means default for reads, 8k for writes, and default for writes. - -.. option:: blocksize_range=irange[,irange][,irange], bsrange=irange[,irange][,irange] - - A range of block sizes in bytes for I/O units. The issued I/O unit will - always be a multiple of the minimum size, unless - :option:`blocksize_unaligned` is set. - - Comma-separated ranges may be specified for reads, writes, and trims as - described in :option:`blocksize`. - - Example: ``bsrange=1k-4k,2k-8k``. - -.. option:: bssplit=str[,str][,str] - - Sometimes you want even finer grained control of the block sizes issued, not - just an even split between them. This option allows you to weight various - block sizes, so that you are able to define a specific amount of block sizes - issued. The format for this option is:: - - bssplit=blocksize/percentage:blocksize/percentage - - for as many block sizes as needed. So if you want to define a workload that - has 50% 64k blocks, 10% 4k blocks, and 40% 32k blocks, you would write:: - - bssplit=4k/10:64k/50:32k/40 - - Ordering does not matter. If the percentage is left blank, fio will fill in - the remaining values evenly. So a bssplit option like this one:: - - bssplit=4k/50:1k/:32k/ - - would have 50% 4k ios, and 25% 1k and 32k ios. The percentages always add up - to 100, if bssplit is given a range that adds up to more, it will error out. - - Comma-separated values may be specified for reads, writes, and trims as - described in :option:`blocksize`. - - If you want a workload that has 50% 2k reads and 50% 4k reads, while having - 90% 4k writes and 10% 8k writes, you would specify:: - - bssplit=2k/50:4k/50,4k/90,8k/10 - -.. option:: blocksize_unaligned, bs_unaligned - - If set, fio will issue I/O units with any size within - :option:`blocksize_range`, not just multiples of the minimum size. This - typically won't work with direct I/O, as that normally requires sector - alignment. - -.. option:: bs_is_seq_rand - - If this option is set, fio will use the normal read,write blocksize settings - as sequential,random blocksize settings instead. Any random read or write - will use the WRITE blocksize settings, and any sequential read or write will - use the READ blocksize settings. - -.. option:: blockalign=int[,int][,int], ba=int[,int][,int] - - Boundary to which fio will align random I/O units. Default: - :option:`blocksize`. Minimum alignment is typically 512b for using direct - I/O, though it usually depends on the hardware block size. This option is - mutually exclusive with using a random map for files, so it will turn off - that option. Comma-separated values may be specified for reads, writes, and - trims as described in :option:`blocksize`. - - -Buffers and memory -~~~~~~~~~~~~~~~~~~ - -.. option:: zero_buffers - - Initialize buffers with all zeros. Default: fill buffers with random data. - -.. option:: refill_buffers - - If this option is given, fio will refill the I/O buffers on every - submit. The default is to only fill it at init time and reuse that - data. Only makes sense if zero_buffers isn't specified, naturally. If data - verification is enabled, `refill_buffers` is also automatically enabled. - -.. option:: scramble_buffers=bool - - If :option:`refill_buffers` is too costly and the target is using data - deduplication, then setting this option will slightly modify the I/O buffer - contents to defeat normal de-dupe attempts. This is not enough to defeat - more clever block compression attempts, but it will stop naive dedupe of - blocks. Default: true. - -.. option:: buffer_compress_percentage=int - - If this is set, then fio will attempt to provide I/O buffer content (on - WRITEs) that compress to the specified level. Fio does this by providing a - mix of random data and a fixed pattern. The fixed pattern is either zeroes, - or the pattern specified by :option:`buffer_pattern`. If the pattern option - is used, it might skew the compression ratio slightly. Note that this is per - block size unit, for file/disk wide compression level that matches this - setting, you'll also want to set :option:`refill_buffers`. - -.. option:: buffer_compress_chunk=int - - See :option:`buffer_compress_percentage`. This setting allows fio to manage - how big the ranges of random data and zeroed data is. Without this set, fio - will provide :option:`buffer_compress_percentage` of blocksize random data, - followed by the remaining zeroed. With this set to some chunk size smaller - than the block size, fio can alternate random and zeroed data throughout the - I/O buffer. - -.. option:: buffer_pattern=str - - If set, fio will fill the I/O buffers with this pattern. If not set, the - contents of I/O buffers is defined by the other options related to buffer - contents. The setting can be any pattern of bytes, and can be prefixed with - 0x for hex values. It may also be a string, where the string must then be - wrapped with ``""``, e.g.:: - - buffer_pattern="abcd" - - or:: - - buffer_pattern=-12 - - or:: - - buffer_pattern=0xdeadface - - Also you can combine everything together in any order:: - - buffer_pattern=0xdeadface"abcd"-12 - -.. option:: dedupe_percentage=int - - If set, fio will generate this percentage of identical buffers when - writing. These buffers will be naturally dedupable. The contents of the - buffers depend on what other buffer compression settings have been set. It's - possible to have the individual buffers either fully compressible, or not at - all. This option only controls the distribution of unique buffers. - -.. option:: invalidate=bool - - Invalidate the buffer/page cache parts for this file prior to starting - I/O if the platform and file type support it. Defaults to true. - This will be ignored if :option:`pre_read` is also specified for the - same job. - -.. option:: sync=bool - - Use synchronous I/O for buffered writes. For the majority of I/O engines, - this means using O_SYNC. Default: false. - -.. option:: iomem=str, mem=str - - Fio can use various types of memory as the I/O unit buffer. The allowed - values are: - - **malloc** - Use memory from :manpage:`malloc(3)` as the buffers. Default memory - type. - - **shm** - Use shared memory as the buffers. Allocated through - :manpage:`shmget(2)`. - - **shmhuge** - Same as shm, but use huge pages as backing. - - **mmap** - Use mmap to allocate buffers. May either be anonymous memory, or can - be file backed if a filename is given after the option. The format - is `mem=mmap:/path/to/file`. - - **mmaphuge** - Use a memory mapped huge file as the buffer backing. Append filename - after mmaphuge, ala `mem=mmaphuge:/hugetlbfs/file`. - - **mmapshared** - Same as mmap, but use a MMAP_SHARED mapping. - - **cudamalloc** - Use GPU memory as the buffers for GPUDirect RDMA benchmark. - - The area allocated is a function of the maximum allowed bs size for the job, - multiplied by the I/O depth given. Note that for **shmhuge** and - **mmaphuge** to work, the system must have free huge pages allocated. This - can normally be checked and set by reading/writing - :file:`/proc/sys/vm/nr_hugepages` on a Linux system. Fio assumes a huge page - is 4MiB in size. So to calculate the number of huge pages you need for a - given job file, add up the I/O depth of all jobs (normally one unless - :option:`iodepth` is used) and multiply by the maximum bs set. Then divide - that number by the huge page size. You can see the size of the huge pages in - :file:`/proc/meminfo`. If no huge pages are allocated by having a non-zero - number in `nr_hugepages`, using **mmaphuge** or **shmhuge** will fail. Also - see :option:`hugepage-size`. - - **mmaphuge** also needs to have hugetlbfs mounted and the file location - should point there. So if it's mounted in :file:`/huge`, you would use - `mem=mmaphuge:/huge/somefile`. - -.. option:: iomem_align=int - - This indicates the memory alignment of the I/O memory buffers. Note that - the given alignment is applied to the first I/O unit buffer, if using - :option:`iodepth` the alignment of the following buffers are given by the - :option:`bs` used. In other words, if using a :option:`bs` that is a - multiple of the page sized in the system, all buffers will be aligned to - this value. If using a :option:`bs` that is not page aligned, the alignment - of subsequent I/O memory buffers is the sum of the :option:`iomem_align` and - :option:`bs` used. - -.. option:: hugepage-size=int - - Defines the size of a huge page. Must at least be equal to the system - setting, see :file:`/proc/meminfo`. Defaults to 4MiB. Should probably - always be a multiple of megabytes, so using ``hugepage-size=Xm`` is the - preferred way to set this to avoid setting a non-pow-2 bad value. - -.. option:: lockmem=int - - Pin the specified amount of memory with :manpage:`mlock(2)`. Can be used to - simulate a smaller amount of memory. The amount specified is per worker. - - -I/O size -~~~~~~~~ - -.. option:: size=int - - The total size of file I/O for each thread of this job. Fio will run until - this many bytes has been transferred, unless runtime is limited by other options - (such as :option:`runtime`, for instance, or increased/decreased by :option:`io_size`). - Fio will divide this size between the available files determined by options - such as :option:`nrfiles`, :option:`filename`, unless :option:`filesize` is - specified by the job. If the result of division happens to be 0, the size is - set to the physical size of the given files or devices if they exist. - If this option is not specified, fio will use the full size of the given - files or devices. If the files do not exist, size must be given. It is also - possible to give size as a percentage between 1 and 100. If ``size=20%`` is - given, fio will use 20% of the full size of the given files or devices. - Can be combined with :option:`offset` to constrain the start and end range - that I/O will be done within. - -.. option:: io_size=int, io_limit=int - - Normally fio operates within the region set by :option:`size`, which means - that the :option:`size` option sets both the region and size of I/O to be - performed. Sometimes that is not what you want. With this option, it is - possible to define just the amount of I/O that fio should do. For instance, - if :option:`size` is set to 20GiB and :option:`io_size` is set to 5GiB, fio - will perform I/O within the first 20GiB but exit when 5GiB have been - done. The opposite is also possible -- if :option:`size` is set to 20GiB, - and :option:`io_size` is set to 40GiB, then fio will do 40GiB of I/O within - the 0..20GiB region. - -.. option:: filesize=int - - Individual file sizes. May be a range, in which case fio will select sizes - for files at random within the given range and limited to :option:`size` in - total (if that is given). If not given, each created file is the same size. - This option overrides :option:`size` in terms of file size, which means - this value is used as a fixed size or possible range of each file. - -.. option:: file_append=bool - - Perform I/O after the end of the file. Normally fio will operate within the - size of a file. If this option is set, then fio will append to the file - instead. This has identical behavior to setting :option:`offset` to the size - of a file. This option is ignored on non-regular files. - -.. option:: fill_device=bool, fill_fs=bool - - Sets size to something really large and waits for ENOSPC (no space left on - device) as the terminating condition. Only makes sense with sequential - write. For a read workload, the mount point will be filled first then I/O - started on the result. This option doesn't make sense if operating on a raw - device node, since the size of that is already known by the file system. - Additionally, writing beyond end-of-device will not return ENOSPC there. - - -I/O engine -~~~~~~~~~~ - -.. option:: ioengine=str - - Defines how the job issues I/O to the file. The following types are defined: - - **sync** - Basic :manpage:`read(2)` or :manpage:`write(2)` - I/O. :manpage:`lseek(2)` is used to position the I/O location. - See :option:`fsync` and :option:`fdatasync` for syncing write I/Os. - - **psync** - Basic :manpage:`pread(2)` or :manpage:`pwrite(2)` I/O. Default on - all supported operating systems except for Windows. - - **vsync** - Basic :manpage:`readv(2)` or :manpage:`writev(2)` I/O. Will emulate - queuing by coalescing adjacent I/Os into a single submission. - - **pvsync** - Basic :manpage:`preadv(2)` or :manpage:`pwritev(2)` I/O. - - **pvsync2** - Basic :manpage:`preadv2(2)` or :manpage:`pwritev2(2)` I/O. - - **libaio** - Linux native asynchronous I/O. Note that Linux may only support - queued behaviour with non-buffered I/O (set ``direct=1`` or - ``buffered=0``). - This engine defines engine specific options. - - **posixaio** - POSIX asynchronous I/O using :manpage:`aio_read(3)` and - :manpage:`aio_write(3)`. - - **solarisaio** - Solaris native asynchronous I/O. - - **windowsaio** - Windows native asynchronous I/O. Default on Windows. - - **mmap** - File is memory mapped with :manpage:`mmap(2)` and data copied - to/from using :manpage:`memcpy(3)`. - - **splice** - :manpage:`splice(2)` is used to transfer the data and - :manpage:`vmsplice(2)` to transfer data from user space to the - kernel. - - **sg** - SCSI generic sg v3 I/O. May either be synchronous using the SG_IO - ioctl, or if the target is an sg character device we use - :manpage:`read(2)` and :manpage:`write(2)` for asynchronous - I/O. Requires filename option to specify either block or character - devices. - - **null** - Doesn't transfer any data, just pretends to. This is mainly used to - exercise fio itself and for debugging/testing purposes. - - **net** - Transfer over the network to given ``host:port``. Depending on the - :option:`protocol` used, the :option:`hostname`, :option:`port`, - :option:`listen` and :option:`filename` options are used to specify - what sort of connection to make, while the :option:`protocol` option - determines which protocol will be used. This engine defines engine - specific options. - - **netsplice** - Like **net**, but uses :manpage:`splice(2)` and - :manpage:`vmsplice(2)` to map data and send/receive. - This engine defines engine specific options. - - **cpuio** - Doesn't transfer any data, but burns CPU cycles according to the - :option:`cpuload` and :option:`cpuchunks` options. Setting - :option:`cpuload` =85 will cause that job to do nothing but burn 85% - of the CPU. In case of SMP machines, use :option:`numjobs` - =<no_of_cpu> to get desired CPU usage, as the cpuload only loads a - single CPU at the desired rate. A job never finishes unless there is - at least one non-cpuio job. - - **guasi** - The GUASI I/O engine is the Generic Userspace Asyncronous Syscall - Interface approach to async I/O. See - - http://www.xmailserver.org/guasi-lib.html - - for more info on GUASI. - - **rdma** - The RDMA I/O engine supports both RDMA memory semantics - (RDMA_WRITE/RDMA_READ) and channel semantics (Send/Recv) for the - InfiniBand, RoCE and iWARP protocols. - - **falloc** - I/O engine that does regular fallocate to simulate data transfer as - fio ioengine. - - DDIR_READ - does fallocate(,mode = FALLOC_FL_KEEP_SIZE,). - - DDIR_WRITE - does fallocate(,mode = 0). - - DDIR_TRIM - does fallocate(,mode = FALLOC_FL_KEEP_SIZE|FALLOC_FL_PUNCH_HOLE). - - **ftruncate** - I/O engine that sends :manpage:`ftruncate(2)` operations in response - to write (DDIR_WRITE) events. Each ftruncate issued sets the file's - size to the current block offset. Block size is ignored. - - **e4defrag** - I/O engine that does regular EXT4_IOC_MOVE_EXT ioctls to simulate - defragment activity in request to DDIR_WRITE event. - - **rbd** - I/O engine supporting direct access to Ceph Rados Block Devices - (RBD) via librbd without the need to use the kernel rbd driver. This - ioengine defines engine specific options. - - **gfapi** - Using Glusterfs libgfapi sync interface to direct access to - Glusterfs volumes without having to go through FUSE. This ioengine - defines engine specific options. - - **gfapi_async** - Using Glusterfs libgfapi async interface to direct access to - Glusterfs volumes without having to go through FUSE. This ioengine - defines engine specific options. - - **libhdfs** - Read and write through Hadoop (HDFS). The :file:`filename` option - is used to specify host,port of the hdfs name-node to connect. This - engine interprets offsets a little differently. In HDFS, files once - created cannot be modified. So random writes are not possible. To - imitate this, libhdfs engine expects bunch of small files to be - created over HDFS, and engine will randomly pick a file out of those - files based on the offset generated by fio backend. (see the example - job file to create such files, use ``rw=write`` option). Please - note, you might want to set necessary environment variables to work - with hdfs/libhdfs properly. Each job uses its own connection to - HDFS. - - **mtd** - Read, write and erase an MTD character device (e.g., - :file:`/dev/mtd0`). Discards are treated as erases. Depending on the - underlying device type, the I/O may have to go in a certain pattern, - e.g., on NAND, writing sequentially to erase blocks and discarding - before overwriting. The writetrim mode works well for this - constraint. - - **pmemblk** - Read and write using filesystem DAX to a file on a filesystem - mounted with DAX on a persistent memory device through the NVML - libpmemblk library. - - **dev-dax** - Read and write using device DAX to a persistent memory device (e.g., - /dev/dax0.0) through the NVML libpmem library. - - **external** - Prefix to specify loading an external I/O engine object file. Append - the engine filename, e.g. ``ioengine=external:/tmp/foo.o`` to load - ioengine :file:`foo.o` in :file:`/tmp`. - - -I/O engine specific parameters -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -In addition, there are some parameters which are only valid when a specific -ioengine is in use. These are used identically to normal parameters, with the -caveat that when used on the command line, they must come after the -:option:`ioengine` that defines them is selected. - -.. option:: userspace_reap : [libaio] - - Normally, with the libaio engine in use, fio will use the - :manpage:`io_getevents(2)` system call to reap newly returned events. With - this flag turned on, the AIO ring will be read directly from user-space to - reap events. The reaping mode is only enabled when polling for a minimum of - 0 events (e.g. when :option:`iodepth_batch_complete` `=0`). - -.. option:: hipri : [pvsync2] - - Set RWF_HIPRI on I/O, indicating to the kernel that it's of higher priority - than normal. - -.. option:: cpuload=int : [cpuio] - - Attempt to use the specified percentage of CPU cycles. This is a mandatory - option when using cpuio I/O engine. - -.. option:: cpuchunks=int : [cpuio] - - Split the load into cycles of the given time. In microseconds. - -.. option:: exit_on_io_done=bool : [cpuio] - - Detect when I/O threads are done, then exit. - -.. option:: hostname=str : [netsplice] [net] - - The host name or IP address to use for TCP or UDP based I/O. If the job is - a TCP listener or UDP reader, the host name is not used and must be omitted - unless it is a valid UDP multicast address. - -.. option:: namenode=str : [libhdfs] - - The host name or IP address of a HDFS cluster namenode to contact. - -.. option:: port=int - - [netsplice], [net] - - The TCP or UDP port to bind to or connect to. If this is used with - :option:`numjobs` to spawn multiple instances of the same job type, then - this will be the starting port number since fio will use a range of - ports. - - [libhdfs] - - the listening port of the HFDS cluster namenode. - -.. option:: interface=str : [netsplice] [net] - - The IP address of the network interface used to send or receive UDP - multicast. - -.. option:: ttl=int : [netsplice] [net] - - Time-to-live value for outgoing UDP multicast packets. Default: 1. - -.. option:: nodelay=bool : [netsplice] [net] - - Set TCP_NODELAY on TCP connections. - -.. option:: protocol=str : [netsplice] [net] - -.. option:: proto=str : [netsplice] [net] - - The network protocol to use. Accepted values are: - - **tcp** - Transmission control protocol. - **tcpv6** - Transmission control protocol V6. - **udp** - User datagram protocol. - **udpv6** - User datagram protocol V6. - **unix** - UNIX domain socket. - - When the protocol is TCP or UDP, the port must also be given, as well as the - hostname if the job is a TCP listener or UDP reader. For unix sockets, the - normal filename option should be used and the port is invalid. - -.. option:: listen : [net] - - For TCP network connections, tell fio to listen for incoming connections - rather than initiating an outgoing connection. The :option:`hostname` must - be omitted if this option is used. - -.. option:: pingpong : [net] - - Normally a network writer will just continue writing data, and a network - reader will just consume packages. If ``pingpong=1`` is set, a writer will - send its normal payload to the reader, then wait for the reader to send the - same payload back. This allows fio to measure network latencies. The - submission and completion latencies then measure local time spent sending or - receiving, and the completion latency measures how long it took for the - other end to receive and send back. For UDP multicast traffic - ``pingpong=1`` should only be set for a single reader when multiple readers - are listening to the same address. - -.. option:: window_size : [net] - - Set the desired socket buffer size for the connection. - -.. option:: mss : [net] - - Set the TCP maximum segment size (TCP_MAXSEG). - -.. option:: donorname=str : [e4defrag] - - File will be used as a block donor(swap extents between files). - -.. option:: inplace=int : [e4defrag] - - Configure donor file blocks allocation strategy: - - **0** - Default. Preallocate donor's file on init. - **1** - Allocate space immediately inside defragment event, and free right - after event. - -.. option:: clustername=str : [rbd] - - Specifies the name of the Ceph cluster. - -.. option:: rbdname=str : [rbd] - - Specifies the name of the RBD. - -.. option:: pool=str : [rbd] - - Specifies the name of the Ceph pool containing RBD. - -.. option:: clientname=str : [rbd] - - Specifies the username (without the 'client.' prefix) used to access the - Ceph cluster. If the *clustername* is specified, the *clientname* shall be - the full *type.id* string. If no type. prefix is given, fio will add - 'client.' by default. - -.. option:: skip_bad=bool : [mtd] - - Skip operations against known bad blocks. - -.. option:: hdfsdirectory : [libhdfs] - - libhdfs will create chunk in this HDFS directory. - -.. option:: chunk_size : [libhdfs] - - the size of the chunk to use for each file. - - -I/O depth -~~~~~~~~~ - -.. option:: iodepth=int - - Number of I/O units to keep in flight against the file. Note that - increasing *iodepth* beyond 1 will not affect synchronous ioengines (except - for small degrees when :option:`verify_async` is in use). Even async - engines may impose OS restrictions causing the desired depth not to be - achieved. This may happen on Linux when using libaio and not setting - :option:`direct` =1, since buffered I/O is not async on that OS. Keep an - eye on the I/O depth distribution in the fio output to verify that the - achieved depth is as expected. Default: 1. - -.. option:: iodepth_batch_submit=int, iodepth_batch=int - - This defines how many pieces of I/O to submit at once. It defaults to 1 - which means that we submit each I/O as soon as it is available, but can be - raised to submit bigger batches of I/O at the time. If it is set to 0 the - :option:`iodepth` value will be used. - -.. option:: iodepth_batch_complete_min=int, iodepth_batch_complete=int - - This defines how many pieces of I/O to retrieve at once. It defaults to 1 - which means that we'll ask for a minimum of 1 I/O in the retrieval process - from the kernel. The I/O retrieval will go on until we hit the limit set by - :option:`iodepth_low`. If this variable is set to 0, then fio will always - check for completed events before queuing more I/O. This helps reduce I/O - latency, at the cost of more retrieval system calls. - -.. option:: iodepth_batch_complete_max=int - - This defines maximum pieces of I/O to retrieve at once. This variable should - be used along with :option:`iodepth_batch_complete_min` =int variable, - specifying the range of min and max amount of I/O which should be - retrieved. By default it is equal to :option:`iodepth_batch_complete_min` - value. - - Example #1:: - - iodepth_batch_complete_min=1 - iodepth_batch_complete_max=<iodepth> - - which means that we will retrieve at least 1 I/O and up to the whole - submitted queue depth. If none of I/O has been completed yet, we will wait. - - Example #2:: - - iodepth_batch_complete_min=0 - iodepth_batch_complete_max=<iodepth> - - which means that we can retrieve up to the whole submitted queue depth, but - if none of I/O has been completed yet, we will NOT wait and immediately exit - the system call. In this example we simply do polling. - -.. option:: iodepth_low=int - - The low water mark indicating when to start filling the queue - again. Defaults to the same as :option:`iodepth`, meaning that fio will - attempt to keep the queue full at all times. If :option:`iodepth` is set to - e.g. 16 and *iodepth_low* is set to 4, then after fio has filled the queue of - 16 requests, it will let the depth drain down to 4 before starting to fill - it again. - -.. option:: io_submit_mode=str - - This option controls how fio submits the I/O to the I/O engine. The default - is `inline`, which means that the fio job threads submit and reap I/O - directly. If set to `offload`, the job threads will offload I/O submission - to a dedicated pool of I/O threads. This requires some coordination and thus - has a bit of extra overhead, especially for lower queue depth I/O where it - can increase latencies. The benefit is that fio can manage submission rates - independently of the device completion rates. This avoids skewed latency - reporting if I/O gets back up on the device side (the coordinated omission - problem). - - -I/O rate -~~~~~~~~ - -.. option:: thinktime=time - - Stall the job for the specified period of time after an I/O has completed before issuing the - next. May be used to simulate processing being done by an application. - When the unit is omitted, the value is given in microseconds. See - :option:`thinktime_blocks` and :option:`thinktime_spin`. - -.. option:: thinktime_spin=time - - Only valid if :option:`thinktime` is set - pretend to spend CPU time doing - something with the data received, before falling back to sleeping for the - rest of the period specified by :option:`thinktime`. When the unit is - omitted, the value is given in microseconds. - -.. option:: thinktime_blocks=int - - Only valid if :option:`thinktime` is set - control how many blocks to issue, - before waiting `thinktime` usecs. If not set, defaults to 1 which will make - fio wait `thinktime` usecs after every block. This effectively makes any - queue depth setting redundant, since no more than 1 I/O will be queued - before we have to complete it and do our thinktime. In other words, this - setting effectively caps the queue depth if the latter is larger. - -.. option:: rate=int[,int][,int] - - Cap the bandwidth used by this job. The number is in bytes/sec, the normal - suffix rules apply. Comma-separated values may be specified for reads, - writes, and trims as described in :option:`blocksize`. - -.. option:: rate_min=int[,int][,int] - - Tell fio to do whatever it can to maintain at least this bandwidth. Failing - to meet this requirement will cause the job to exit. Comma-separated values - may be specified for reads, writes, and trims as described in - :option:`blocksize`. - -.. option:: rate_iops=int[,int][,int] - - Cap the bandwidth to this number of IOPS. Basically the same as - :option:`rate`, just specified independently of bandwidth. If the job is - given a block size range instead of a fixed value, the smallest block size - is used as the metric. Comma-separated values may be specified for reads, - writes, and trims as described in :option:`blocksize`. - -.. option:: rate_iops_min=int[,int][,int] - - If fio doesn't meet this rate of I/O, it will cause the job to exit. - Comma-separated values may be specified for reads, writes, and trims as - described in :option:`blocksize`. - -.. option:: rate_process=str - - This option controls how fio manages rated I/O submissions. The default is - `linear`, which submits I/O in a linear fashion with fixed delays between - I/Os that gets adjusted based on I/O completion rates. If this is set to - `poisson`, fio will submit I/O based on a more real world random request - flow, known as the Poisson process - (https://en.wikipedia.org/wiki/Poisson_point_process). The lambda will be - 10^6 / IOPS for the given workload. - - -I/O latency -~~~~~~~~~~~ - -.. option:: latency_target=time - - If set, fio will attempt to find the max performance point that the given - workload will run at while maintaining a latency below this target. When - the unit is omitted, the value is given in microseconds. See - :option:`latency_window` and :option:`latency_percentile`. - -.. option:: latency_window=time - - Used with :option:`latency_target` to specify the sample window that the job - is run at varying queue depths to test the performance. When the unit is - omitted, the value is given in microseconds. - -.. option:: latency_percentile=float - - The percentage of I/Os that must fall within the criteria specified by - :option:`latency_target` and :option:`latency_window`. If not set, this - defaults to 100.0, meaning that all I/Os must be equal or below to the value - set by :option:`latency_target`. - -.. option:: max_latency=time - - If set, fio will exit the job with an ETIMEDOUT error if it exceeds this - maximum latency. When the unit is omitted, the value is given in - microseconds. - -.. option:: rate_cycle=int - - Average bandwidth for :option:`rate` and :option:`rate_min` over this number - of milliseconds. - - -I/O replay -~~~~~~~~~~ - -.. option:: write_iolog=str - - Write the issued I/O patterns to the specified file. See - :option:`read_iolog`. Specify a separate file for each job, otherwise the - iologs will be interspersed and the file may be corrupt. - -.. option:: read_iolog=str - - Open an iolog with the specified file name and replay the I/O patterns it - contains. This can be used to store a workload and replay it sometime - later. The iolog given may also be a blktrace binary file, which allows fio - to replay a workload captured by :command:`blktrace`. See - :manpage:`blktrace(8)` for how to capture such logging data. For blktrace - replay, the file needs to be turned into a blkparse binary data file first - (``blkparse <device> -o /dev/null -d file_for_fio.bin``). - -.. option:: replay_no_stall=int - - When replaying I/O with :option:`read_iolog` the default behavior is to - attempt to respect the time stamps within the log and replay them with the - appropriate delay between IOPS. By setting this variable fio will not - respect the timestamps and attempt to replay them as fast as possible while - still respecting ordering. The result is the same I/O pattern to a given - device, but different timings. - -.. option:: replay_redirect=str - - While replaying I/O patterns using :option:`read_iolog` the default behavior - is to replay the IOPS onto the major/minor device that each IOP was recorded - from. This is sometimes undesirable because on a different machine those - major/minor numbers can map to a different device. Changing hardware on the - same system can also result in a different major/minor mapping. - ``replay_redirect`` causes all IOPS to be replayed onto the single specified - device regardless of the device it was recorded - from. i.e. :option:`replay_redirect` = :file:`/dev/sdc` would cause all I/O - in the blktrace or iolog to be replayed onto :file:`/dev/sdc`. This means - multiple devices will be replayed onto a single device, if the trace - contains multiple devices. If you want multiple devices to be replayed - concurrently to multiple redirected devices you must blkparse your trace - into separate traces and replay them with independent fio invocations. - Unfortunately this also breaks the strict time ordering between multiple - device accesses. - -.. option:: replay_align=int - - Force alignment of I/O offsets and lengths in a trace to this power of 2 - value. - -.. option:: replay_scale=int - - Scale sector offsets down by this factor when replaying traces. - - -Threads, processes and job synchronization -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -.. option:: thread - - Fio defaults to forking jobs, however if this option is given, fio will use - POSIX Threads function :manpage:`pthread_create(3)` to create threads instead - of forking processes. - -.. option:: wait_for=str - - Specifies the name of the already defined job to wait for. Single waitee - name only may be specified. If set, the job won't be started until all - workers of the waitee job are done. - - ``wait_for`` operates on the job name basis, so there are a few - limitations. First, the waitee must be defined prior to the waiter job - (meaning no forward references). Second, if a job is being referenced as a - waitee, it must have a unique name (no duplicate waitees). - -.. option:: nice=int - - Run the job with the given nice value. See man :manpage:`nice(2)`. - - On Windows, values less than -15 set the process class to "High"; -1 through - -15 set "Above Normal"; 1 through 15 "Below Normal"; and above 15 "Idle" - priority class. - -.. option:: prio=int - - Set the I/O priority value of this job. Linux limits us to a positive value - between 0 and 7, with 0 being the highest. See man - :manpage:`ionice(1)`. Refer to an appropriate manpage for other operating - systems since meaning of priority may differ. - -.. option:: prioclass=int - - Set the I/O priority class. See man :manpage:`ionice(1)`. - -.. option:: cpumask=int - - Set the CPU affinity of this job. The parameter given is a bitmask of - allowed CPU's the job may run on. So if you want the allowed CPUs to be 1 - and 5, you would pass the decimal value of (1 << 1 | 1 << 5), or 34. See man - :manpage:`sched_setaffinity(2)`. This may not work on all supported - operating systems or kernel versions. This option doesn't work well for a - higher CPU count than what you can store in an integer mask, so it can only - control cpus 1-32. For boxes with larger CPU counts, use - :option:`cpus_allowed`. - -.. option:: cpus_allowed=str - - Controls the same options as :option:`cpumask`, but it allows a text setting - of the permitted CPUs instead. So to use CPUs 1 and 5, you would specify - ``cpus_allowed=1,5``. This options also allows a range of CPUs. Say you - wanted a binding to CPUs 1, 5, and 8-15, you would set - ``cpus_allowed=1,5,8-15``. - -.. option:: cpus_allowed_policy=str - - Set the policy of how fio distributes the CPUs specified by - :option:`cpus_allowed` or cpumask. Two policies are supported: - - **shared** - All jobs will share the CPU set specified. - **split** - Each job will get a unique CPU from the CPU set. - - **shared** is the default behaviour, if the option isn't specified. If - **split** is specified, then fio will will assign one cpu per job. If not - enough CPUs are given for the jobs listed, then fio will roundrobin the CPUs - in the set. - -.. option:: numa_cpu_nodes=str - - Set this job running on specified NUMA nodes' CPUs. The arguments allow - comma delimited list of cpu numbers, A-B ranges, or `all`. Note, to enable - numa options support, fio must be built on a system with libnuma-dev(el) - installed. - -.. option:: numa_mem_policy=str - - Set this job's memory policy and corresponding NUMA nodes. Format of the - arguments:: - - <mode>[:<nodelist>] - - ``mode`` is one of the following memory policy: ``default``, ``prefer``, - ``bind``, ``interleave``, ``local`` For ``default`` and ``local`` memory - policy, no node is needed to be specified. For ``prefer``, only one node is - allowed. For ``bind`` and ``interleave``, it allow comma delimited list of - numbers, A-B ranges, or `all`. - -.. option:: cgroup=str - - Add job to this control group. If it doesn't exist, it will be created. The - system must have a mounted cgroup blkio mount point for this to work. If - your system doesn't have it mounted, you can do so with:: - - # mount -t cgroup -o blkio none /cgroup - -.. option:: cgroup_weight=int - - Set the weight of the cgroup to this value. See the documentation that comes - with the kernel, allowed values are in the range of 100..1000. - -.. option:: cgroup_nodelete=bool - - Normally fio will delete the cgroups it has created after the job - completion. To override this behavior and to leave cgroups around after the - job completion, set ``cgroup_nodelete=1``. This can be useful if one wants - to inspect various cgroup files after job completion. Default: false. - -.. option:: flow_id=int - - The ID of the flow. If not specified, it defaults to being a global - flow. See :option:`flow`. - -.. option:: flow=int - - Weight in token-based flow control. If this value is used, then there is a - 'flow counter' which is used to regulate the proportion of activity between - two or more jobs. Fio attempts to keep this flow counter near zero. The - ``flow`` parameter stands for how much should be added or subtracted to the - flow counter on each iteration of the main I/O loop. That is, if one job has - ``flow=8`` and another job has ``flow=-1``, then there will be a roughly 1:8 - ratio in how much one runs vs the other. - -.. option:: flow_watermark=int - - The maximum value that the absolute value of the flow counter is allowed to - reach before the job must wait for a lower value of the counter. - -.. option:: flow_sleep=int - - The period of time, in microseconds, to wait after the flow watermark has - been exceeded before retrying operations. - -.. option:: stonewall, wait_for_previous - - Wait for preceding jobs in the job file to exit, before starting this - one. Can be used to insert serialization points in the job file. A stone - wall also implies starting a new reporting group, see - :option:`group_reporting`. - -.. option:: exitall - - When one job finishes, terminate the rest. The default is to wait for each - job to finish, sometimes that is not the desired action. - -.. option:: exec_prerun=str - - Before running this job, issue the command specified through - :manpage:`system(3)`. Output is redirected in a file called - :file:`jobname.prerun.txt`. - -.. option:: exec_postrun=str - - After the job completes, issue the command specified though - :manpage:`system(3)`. Output is redirected in a file called - :file:`jobname.postrun.txt`. - -.. option:: uid=int - - Instead of running as the invoking user, set the user ID to this value - before the thread/process does any work. - -.. option:: gid=int - - Set group ID, see :option:`uid`. - - -Verification -~~~~~~~~~~~~ - -.. option:: verify_only - - Do not perform specified workload, only verify data still matches previous - invocation of this workload. This option allows one to check data multiple - times at a later date without overwriting it. This option makes sense only - for workloads that write data, and does not support workloads with the - :option:`time_based` option set. - -.. option:: do_verify=bool - - Run the verify phase after a write phase. Only valid if :option:`verify` is - set. Default: true. - -.. option:: verify=str - - If writing to a file, fio can verify the file contents after each iteration - of the job. Each verification method also implies verification of special - header, which is written to the beginning of each block. This header also - includes meta information, like offset of the block, block number, timestamp - when block was written, etc. :option:`verify` can be combined with - :option:`verify_pattern` option. The allowed values are: - - **md5** - Use an md5 sum of the data area and store it in the header of - each block. - - **crc64** - Use an experimental crc64 sum of the data area and store it in the - header of each block. - - **crc32c** - Use a crc32c sum of the data area and store it in the header of each - block. - - **crc32c-intel** - Use hardware assisted crc32c calculation provided on SSE4.2 enabled - processors. Falls back to regular software crc32c, if not supported - by the system. - - **crc32** - Use a crc32 sum of the data area and store it in the header of each - block. - - **crc16** - Use a crc16 sum of the data area and store it in the header of each - block. - - **crc7** - Use a crc7 sum of the data area and store it in the header of each - block. - - **xxhash** - Use xxhash as the checksum function. Generally the fastest software - checksum that fio supports. - - **sha512** - Use sha512 as the checksum function. - - **sha256** - Use sha256 as the checksum function. - - **sha1** - Use optimized sha1 as the checksum function. - - **sha3-224** - Use optimized sha3-224 as the checksum function. - - **sha3-256** - Use optimized sha3-256 as the checksum function. - - **sha3-384** - Use optimized sha3-384 as the checksum function. - - **sha3-512** - Use optimized sha3-512 as the checksum function. - - **meta** - This option is deprecated, since now meta information is included in - generic verification header and meta verification happens by - default. For detailed information see the description of the - :option:`verify` setting. This option is kept because of - compatibility's sake with old configurations. Do not use it. - - **pattern** - Verify a strict pattern. Normally fio includes a header with some - basic information and checksumming, but if this option is set, only - the specific pattern set with :option:`verify_pattern` is verified. - - **null** - Only pretend to verify. Useful for testing internals with - :option:`ioengine` `=null`, not for much else. - - This option can be used for repeated burn-in tests of a system to make sure - that the written data is also correctly read back. If the data direction - given is a read or random read, fio will assume that it should verify a - previously written file. If the data direction includes any form of write, - the verify will be of the newly written data. - -.. option:: verifysort=bool - - If true, fio will sort written verify blocks when it deems it faster to read - them back in a sorted manner. This is often the case when overwriting an - existing file, since the blocks are already laid out in the file system. You - can ignore this option unless doing huge amounts of really fast I/O where - the red-black tree sorting CPU time becomes significant. Default: true. - -.. option:: verifysort_nr=int - - Pre-load and sort verify blocks for a read workload. - -.. option:: verify_offset=int - - Swap the verification header with data somewhere else in the block before - writing. It is swapped back before verifying. - -.. option:: verify_interval=int - - Write the verification header at a finer granularity than the - :option:`blocksize`. It will be written for chunks the size of - ``verify_interval``. :option:`blocksize` should divide this evenly. - -.. option:: verify_pattern=str - - If set, fio will fill the I/O buffers with this pattern. Fio defaults to - filling with totally random bytes, but sometimes it's interesting to fill - with a known pattern for I/O verification purposes. Depending on the width - of the pattern, fio will fill 1/2/3/4 bytes of the buffer at the time(it can - be either a decimal or a hex number). The ``verify_pattern`` if larger than - a 32-bit quantity has to be a hex number that starts with either "0x" or - "0X". Use with :option:`verify`. Also, ``verify_pattern`` supports %o - format, which means that for each block offset will be written and then - verified back, e.g.:: - - verify_pattern=%o - - Or use combination of everything:: - - verify_pattern=0xff%o"abcd"-12 - -.. option:: verify_fatal=bool - - Normally fio will keep checking the entire contents before quitting on a - block verification failure. If this option is set, fio will exit the job on - the first observed failure. Default: false. - -.. option:: verify_dump=bool - - If set, dump the contents of both the original data block and the data block - we read off disk to files. This allows later analysis to inspect just what - kind of data corruption occurred. Off by default. - -.. option:: verify_async=int - - Fio will normally verify I/O inline from the submitting thread. This option - takes an integer describing how many async offload threads to create for I/O - verification instead, causing fio to offload the duty of verifying I/O - contents to one or more separate threads. If using this offload option, even - sync I/O engines can benefit from using an :option:`iodepth` setting higher - than 1, as it allows them to have I/O in flight while verifies are running. - -.. option:: verify_async_cpus=str - - Tell fio to set the given CPU affinity on the async I/O verification - threads. See :option:`cpus_allowed` for the format used. - -.. option:: verify_backlog=int - - Fio will normally verify the written contents of a job that utilizes verify - once that job has completed. In other words, everything is written then - everything is read back and verified. You may want to verify continually - instead for a variety of reasons. Fio stores the meta data associated with - an I/O block in memory, so for large verify workloads, quite a bit of memory - would be used up holding this meta data. If this option is enabled, fio will - write only N blocks before verifying these blocks. - -.. option:: verify_backlog_batch=int - - Control how many blocks fio will verify if :option:`verify_backlog` is - set. If not set, will default to the value of :option:`verify_backlog` - (meaning the entire queue is read back and verified). If - ``verify_backlog_batch`` is less than :option:`verify_backlog` then not all - blocks will be verified, if ``verify_backlog_batch`` is larger than - :option:`verify_backlog`, some blocks will be verified more than once. - -.. option:: verify_state_save=bool - - When a job exits during the write phase of a verify workload, save its - current state. This allows fio to replay up until that point, if the verify - state is loaded for the verify read phase. The format of the filename is, - roughly:: - - <type>-<jobname>-<jobindex>-verify.state. - - <type> is "local" for a local run, "sock" for a client/server socket - connection, and "ip" (192.168.0.1, for instance) for a networked - client/server connection. - -.. option:: verify_state_load=bool - - If a verify termination trigger was used, fio stores the current write state - of each thread. This can be used at verification time so that fio knows how - far it should verify. Without this information, fio will run a full - verification pass, according to the settings in the job file used. - -.. option:: trim_percentage=int - - Number of verify blocks to discard/trim. - -.. option:: trim_verify_zero=bool - - Verify that trim/discarded blocks are returned as zeroes. - -.. option:: trim_backlog=int - - Verify that trim/discarded blocks are returned as zeroes. - -.. option:: trim_backlog_batch=int - - Trim this number of I/O blocks. - -.. option:: experimental_verify=bool - - Enable experimental verification. - - -Steady state -~~~~~~~~~~~~ - -.. option:: steadystate=str:float, ss=str:float - - Define the criterion and limit for assessing steady state performance. The - first parameter designates the criterion whereas the second parameter sets - the threshold. When the criterion falls below the threshold for the - specified duration, the job will stop. For example, `iops_slope:0.1%` will - direct fio to terminate the job when the least squares regression slope - falls below 0.1% of the mean IOPS. If :option:`group_reporting` is enabled - this will apply to all jobs in the group. Below is the list of available - steady state assessment criteria. All assessments are carried out using only - data from the rolling collection window. Threshold limits can be expressed - as a fixed value or as a percentage of the mean in the collection window. - - **iops** - Collect IOPS data. Stop the job if all individual IOPS measurements - are within the specified limit of the mean IOPS (e.g., ``iops:2`` - means that all individual IOPS values must be within 2 of the mean, - whereas ``iops:0.2%`` means that all individual IOPS values must be - within 0.2% of the mean IOPS to terminate the job). - - **iops_slope** - Collect IOPS data and calculate the least squares regression - slope. Stop the job if the slope falls below the specified limit. - - **bw** - Collect bandwidth data. Stop the job if all individual bandwidth - measurements are within the specified limit of the mean bandwidth. - - **bw_slope** - Collect bandwidth data and calculate the least squares regression - slope. Stop the job if the slope falls below the specified limit. - -.. option:: steadystate_duration=time, ss_dur=time - - A rolling window of this duration will be used to judge whether steady state - has been reached. Data will be collected once per second. The default is 0 - which disables steady state detection. When the unit is omitted, the - value is given in seconds. - -.. option:: steadystate_ramp_time=time, ss_ramp=time - - Allow the job to run for the specified duration before beginning data - collection for checking the steady state job termination criterion. The - default is 0. When the unit is omitted, the value is given in seconds. - - -Measurements and reporting -~~~~~~~~~~~~~~~~~~~~~~~~~~ - -.. option:: per_job_logs=bool - - If set, this generates bw/clat/iops log with per file private filenames. If - not set, jobs with identical names will share the log filename. Default: - true. - -.. option:: group_reporting - - It may sometimes be interesting to display statistics for groups of jobs as - a whole instead of for each individual job. This is especially true if - :option:`numjobs` is used; looking at individual thread/process output - quickly becomes unwieldy. To see the final report per-group instead of - per-job, use :option:`group_reporting`. Jobs in a file will be part of the - same reporting group, unless if separated by a :option:`stonewall`, or by - using :option:`new_group`. - -.. option:: new_group - - Start a new reporting group. See: :option:`group_reporting`. If not given, - all jobs in a file will be part of the same reporting group, unless - separated by a :option:`stonewall`. - -.. option:: stats - - By default, fio collects and shows final output results for all jobs - that run. If this option is set to 0, then fio will ignore it in - the final stat output. - -.. option:: write_bw_log=str - - If given, write a bandwidth log for this job. Can be used to store data of - the bandwidth of the jobs in their lifetime. The included - :command:`fio_generate_plots` script uses :command:`gnuplot` to turn these - text files into nice graphs. See :option:`write_lat_log` for behaviour of - given filename. For this option, the postfix is :file:`_bw.x.log`, where `x` - is the index of the job (`1..N`, where `N` is the number of jobs). If - :option:`per_job_logs` is false, then the filename will not include the job - index. See `Log File Formats`_. - -.. option:: write_lat_log=str - - Same as :option:`write_bw_log`, except that this option stores I/O - submission, completion, and total latencies instead. If no filename is given - with this option, the default filename of :file:`jobname_type.log` is - used. Even if the filename is given, fio will still append the type of - log. So if one specifies:: - - write_lat_log=foo - - The actual log names will be :file:`foo_slat.x.log`, :file:`foo_clat.x.log`, - and :file:`foo_lat.x.log`, where `x` is the index of the job (1..N, where N - is the number of jobs). This helps :command:`fio_generate_plot` find the - logs automatically. If :option:`per_job_logs` is false, then the filename - will not include the job index. See `Log File Formats`_. - -.. option:: write_hist_log=str - - Same as :option:`write_lat_log`, but writes I/O completion latency - histograms. If no filename is given with this option, the default filename - of :file:`jobname_clat_hist.x.log` is used, where `x` is the index of the - job (1..N, where `N` is the number of jobs). Even if the filename is given, - fio will still append the type of log. If :option:`per_job_logs` is false, - then the filename will not include the job index. See `Log File Formats`_. - -.. option:: write_iops_log=str - - Same as :option:`write_bw_log`, but writes IOPS. If no filename is given - with this option, the default filename of :file:`jobname_type.x.log` is - used,where `x` is the index of the job (1..N, where `N` is the number of - jobs). Even if the filename is given, fio will still append the type of - log. If :option:`per_job_logs` is false, then the filename will not include - the job index. See `Log File Formats`_. - -.. option:: log_avg_msec=int - - By default, fio will log an entry in the iops, latency, or bw log for every - I/O that completes. When writing to the disk log, that can quickly grow to a - very large size. Setting this option makes fio average the each log entry - over the specified period of time, reducing the resolution of the log. See - :option:`log_max_value` as well. Defaults to 0, logging all entries. - -.. option:: log_hist_msec=int - - Same as :option:`log_avg_msec`, but logs entries for completion latency - histograms. Computing latency percentiles from averages of intervals using - :option:`log_avg_msec` is inaccurate. Setting this option makes fio log - histogram entries over the specified period of time, reducing log sizes for - high IOPS devices while retaining percentile accuracy. See - :option:`log_hist_coarseness` as well. Defaults to 0, meaning histogram - logging is disabled. - -.. option:: log_hist_coarseness=int - - Integer ranging from 0 to 6, defining the coarseness of the resolution of - the histogram logs enabled with :option:`log_hist_msec`. For each increment - in coarseness, fio outputs half as many bins. Defaults to 0, for which - histogram logs contain 1216 latency bins. See `Log File Formats`_. - -.. option:: log_max_value=bool - - If :option:`log_avg_msec` is set, fio logs the average over that window. If - you instead want to log the maximum value, set this option to 1. Defaults to - 0, meaning that averaged values are logged. - -.. option:: log_offset=int - - If this is set, the iolog options will include the byte offset for the I/O - entry as well as the other data values. - -.. option:: log_compression=int - - If this is set, fio will compress the I/O logs as it goes, to keep the - memory footprint lower. When a log reaches the specified size, that chunk is - removed and compressed in the background. Given that I/O logs are fairly - highly compressible, this yields a nice memory savings for longer runs. The - downside is that the compression will consume some background CPU cycles, so - it may impact the run. This, however, is also true if the logging ends up - consuming most of the system memory. So pick your poison. The I/O logs are - saved normally at the end of a run, by decompressing the chunks and storing - them in the specified log file. This feature depends on the availability of - zlib. - -.. option:: log_compression_cpus=str - - Define the set of CPUs that are allowed to handle online log compression for - the I/O jobs. This can provide better isolation between performance - sensitive jobs, and background compression work. - -.. option:: log_store_compressed=bool - - If set, fio will store the log files in a compressed format. They can be - decompressed with fio, using the :option:`--inflate-log` command line - parameter. The files will be stored with a :file:`.fz` suffix. - -.. option:: log_unix_epoch=bool - - If set, fio will log Unix timestamps to the log files produced by enabling - write_type_log for each log type, instead of the default zero-based - timestamps. - -.. option:: block_error_percentiles=bool - - If set, record errors in trim block-sized units from writes and trims and - output a histogram of how many trims it took to get to errors, and what kind - of error was encountered. - -.. option:: bwavgtime=int - - Average the calculated bandwidth over the given time. Value is specified in - milliseconds. If the job also does bandwidth logging through - :option:`write_bw_log`, then the minimum of this option and - :option:`log_avg_msec` will be used. Default: 500ms. - -.. option:: iopsavgtime=int - - Average the calculated IOPS over the given time. Value is specified in - milliseconds. If the job also does IOPS logging through - :option:`write_iops_log`, then the minimum of this option and - :option:`log_avg_msec` will be used. Default: 500ms. - -.. option:: disk_util=bool - - Generate disk utilization statistics, if the platform supports it. - Default: true. - -.. option:: disable_lat=bool - - Disable measurements of total latency numbers. Useful only for cutting back - the number of calls to :manpage:`gettimeofday(2)`, as that does impact - performance at really high IOPS rates. Note that to really get rid of a - large amount of these calls, this option must be used with - :option:`disable_slat` and :option:`disable_bw_measurement` as well. - -.. option:: disable_clat=bool - - Disable measurements of completion latency numbers. See - :option:`disable_lat`. - -.. option:: disable_slat=bool - - Disable measurements of submission latency numbers. See - :option:`disable_slat`. - -.. option:: disable_bw_measurement=bool, disable_bw=bool - - Disable measurements of throughput/bandwidth numbers. See - :option:`disable_lat`. - -.. option:: clat_percentiles=bool - - Enable the reporting of percentiles of completion latencies. - -.. option:: percentile_list=float_list - - Overwrite the default list of percentiles for completion latencies and the - block error histogram. Each number is a floating number in the range - (0,100], and the maximum length of the list is 20. Use ``:`` to separate the - numbers, and list the numbers in ascending order. For example, - ``--percentile_list=99.5:99.9`` will cause fio to report the values of - completion latency below which 99.5% and 99.9% of the observed latencies - fell, respectively. - - -Error handling -~~~~~~~~~~~~~~ - -.. option:: exitall_on_error - - When one job finishes in error, terminate the rest. The default is to wait - for each job to finish. - -.. option:: continue_on_error=str - - Normally fio will exit the job on the first observed failure. If this option - is set, fio will continue the job when there is a 'non-fatal error' (EIO or - EILSEQ) until the runtime is exceeded or the I/O size specified is - completed. If this option is used, there are two more stats that are - appended, the total error count and the first error. The error field given - in the stats is the first error that was hit during the run. - - The allowed values are: - - **none** - Exit on any I/O or verify errors. - - **read** - Continue on read errors, exit on all others. - - **write** - Continue on write errors, exit on all others. - - **io** - Continue on any I/O error, exit on all others. - - **verify** - Continue on verify errors, exit on all others. - - **all** - Continue on all errors. - - **0** - Backward-compatible alias for 'none'. - - **1** - Backward-compatible alias for 'all'. - -.. option:: ignore_error=str - - Sometimes you want to ignore some errors during test in that case you can - specify error list for each error type. - ``ignore_error=READ_ERR_LIST,WRITE_ERR_LIST,VERIFY_ERR_LIST`` errors for - given error type is separated with ':'. Error may be symbol ('ENOSPC', - 'ENOMEM') or integer. Example:: - - ignore_error=EAGAIN,ENOSPC:122 - - This option will ignore EAGAIN from READ, and ENOSPC and 122(EDQUOT) from - WRITE. - -.. option:: error_dump=bool - - If set dump every error even if it is non fatal, true by default. If - disabled only fatal error will be dumped. - -Running predefined workloads ----------------------------- - -Fio includes predefined profiles that mimic the I/O workloads generated by -other tools. - -.. option:: profile=str - - The predefined workload to run. Current profiles are: - - **tiobench** - Threaded I/O bench (tiotest/tiobench) like workload. - - **act** - Aerospike Certification Tool (ACT) like workload. - -To view a profile's additional options use :option:`--cmdhelp` after specifying -the profile. For example:: - -$ fio --profile=act --cmdhelp - -Act profile options -~~~~~~~~~~~~~~~~~~~ - -.. option:: device-names=str - :noindex: - - Devices to use. - -.. option:: load=int - :noindex: - - ACT load multiplier. Default: 1. - -.. option:: test-duration=time - :noindex: - - How long the entire test takes to run. Default: 24h. - -.. option:: threads-per-queue=int - :noindex: - - Number of read IO threads per device. Default: 8. - -.. option:: read-req-num-512-blocks=int - :noindex: - - Number of 512B blocks to read at the time. Default: 3. - -.. option:: large-block-op-kbytes=int - :noindex: - - Size of large block ops in KiB (writes). Default: 131072. - -.. option:: prep - :noindex: - - Set to run ACT prep phase. - -Tiobench profile options -~~~~~~~~~~~~~~~~~~~~~~~~ - -.. option:: size=str - :noindex: - - Size in MiB - -.. option:: block=int - :noindex: - - Block size in bytes. Default: 4096. - -.. option:: numruns=int - :noindex: - - Number of runs. - -.. option:: dir=str - :noindex: - - Test directory. - -.. option:: threads=int - :noindex: - - Number of threads. - -Interpreting the output ------------------------ - -Fio spits out a lot of output. While running, fio will display the status of the -jobs created. An example of that would be:: - - Jobs: 1 (f=1): [_(1),M(1)][24.8%][r=20.5MiB/s,w=23.5MiB/s][r=82,w=94 IOPS][eta 01m:31s] - -The characters inside the square brackets denote the current status of each -thread. The possible values (in typical life cycle order) are: - -+------+-----+-----------------------------------------------------------+ -| Idle | Run | | -+======+=====+===========================================================+ -| P | | Thread setup, but not started. | -+------+-----+-----------------------------------------------------------+ -| C | | Thread created. | -+------+-----+-----------------------------------------------------------+ -| I | | Thread initialized, waiting or generating necessary data. | -+------+-----+-----------------------------------------------------------+ -| | p | Thread running pre-reading file(s). | -+------+-----+-----------------------------------------------------------+ -| | R | Running, doing sequential reads. | -+------+-----+-----------------------------------------------------------+ -| | r | Running, doing random reads. | -+------+-----+-----------------------------------------------------------+ -| | W | Running, doing sequential writes. | -+------+-----+-----------------------------------------------------------+ -| | w | Running, doing random writes. | -+------+-----+-----------------------------------------------------------+ -| | M | Running, doing mixed sequential reads/writes. | -+------+-----+-----------------------------------------------------------+ -| | m | Running, doing mixed random reads/writes. | -+------+-----+-----------------------------------------------------------+ -| | F | Running, currently waiting for :manpage:`fsync(2)` | -+------+-----+-----------------------------------------------------------+ -| | V | Running, doing verification of written data. | -+------+-----+-----------------------------------------------------------+ -| E | | Thread exited, not reaped by main thread yet. | -+------+-----+-----------------------------------------------------------+ -| _ | | Thread reaped, or | -+------+-----+-----------------------------------------------------------+ -| X | | Thread reaped, exited with an error. | -+------+-----+-----------------------------------------------------------+ -| K | | Thread reaped, exited due to signal. | -+------+-----+-----------------------------------------------------------+ - -Fio will condense the thread string as not to take up more space on the command -line as is needed. For instance, if you have 10 readers and 10 writers running, -the output would look like this:: - - Jobs: 20 (f=20): [R(10),W(10)][4.0%][r=20.5MiB/s,w=23.5MiB/s][r=82,w=94 IOPS][eta 57m:36s] - -Fio will still maintain the ordering, though. So the above means that jobs 1..10 -are readers, and 11..20 are writers. - -The other values are fairly self explanatory -- number of threads currently -running and doing I/O, the number of currently open files (f=), the rate of I/O -since last check (read speed listed first, then write speed and optionally trim -speed), and the estimated completion percentage and time for the current -running group. It's impossible to estimate runtime of the following groups (if -any). Note that the string is displayed in order, so it's possible to tell which -of the jobs are currently doing what. The first character is the first job -defined in the job file, and so forth. - -When fio is done (or interrupted by :kbd:`ctrl-c`), it will show the data for -each thread, group of threads, and disks in that order. For each data direction, -the output looks like:: - - Client1 (g=0): err= 0: - write: io= 32MiB, bw= 666KiB/s, iops=89 , runt= 50320msec - slat (msec): min= 0, max= 136, avg= 0.03, stdev= 1.92 - clat (msec): min= 0, max= 631, avg=48.50, stdev=86.82 - bw (KiB/s) : min= 0, max= 1196, per=51.00%, avg=664.02, stdev=681.68 - cpu : usr=1.49%, sys=0.25%, ctx=7969, majf=0, minf=17 - IO depths : 1=0.1%, 2=0.3%, 4=0.5%, 8=99.0%, 16=0.0%, 32=0.0%, >32=0.0% - submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% - complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% - issued r/w: total=0/32768, short=0/0 - lat (msec): 2=1.6%, 4=0.0%, 10=3.2%, 20=12.8%, 50=38.4%, 100=24.8%, - lat (msec): 250=15.2%, 500=0.0%, 750=0.0%, 1000=0.0%, >=2048=0.0% - -The client number is printed, along with the group id and error of that -thread. Below is the I/O statistics, here for writes. In the order listed, they -denote: - -**io** - Number of megabytes I/O performed. - -**bw** - Average bandwidth rate. - -**iops** - Average I/Os performed per second. - -**runt** - The runtime of that thread. - -**slat** - Submission latency (avg being the average, stdev being the standard - deviation). This is the time it took to submit the I/O. For sync I/O, - the slat is really the completion latency, since queue/complete is one - operation there. This value can be in milliseconds or microseconds, fio - will choose the most appropriate base and print that. In the example - above, milliseconds is the best scale. Note: in :option:`--minimal` mode - latencies are always expressed in microseconds. - -**clat** - Completion latency. Same names as slat, this denotes the time from - submission to completion of the I/O pieces. For sync I/O, clat will - usually be equal (or very close) to 0, as the time from submit to - complete is basically just CPU time (I/O has already been done, see slat - explanation). - -**bw** - Bandwidth. Same names as the xlat stats, but also includes an - approximate percentage of total aggregate bandwidth this thread received - in this group. This last value is only really useful if the threads in - this group are on the same disk, since they are then competing for disk - access. - -**cpu** - CPU usage. User and system time, along with the number of context - switches this thread went through, usage of system and user time, and - finally the number of major and minor page faults. The CPU utilization - numbers are averages for the jobs in that reporting group, while the - context and fault counters are summed. - -**IO depths** - The distribution of I/O depths over the job life time. The numbers are - divided into powers of 2, so for example the 16= entries includes depths - up to that value but higher than the previous entry. In other words, it - covers the range from 16 to 31. - -**IO submit** - How many pieces of I/O were submitting in a single submit call. Each - entry denotes that amount and below, until the previous entry -- e.g., - 8=100% mean that we submitted anywhere in between 5-8 I/Os per submit - call. - -**IO complete** - Like the above submit number, but for completions instead. - -**IO issued** - The number of read/write requests issued, and how many of them were - short. - -**IO latencies** - The distribution of I/O completion latencies. This is the time from when - I/O leaves fio and when it gets completed. The numbers follow the same - pattern as the I/O depths, meaning that 2=1.6% means that 1.6% of the - I/O completed within 2 msecs, 20=12.8% means that 12.8% of the I/O took - more than 10 msecs, but less than (or equal to) 20 msecs. - -After each client has been listed, the group statistics are printed. They -will look like this:: - - Run status group 0 (all jobs): - READ: io=64MB, aggrb=22178, minb=11355, maxb=11814, mint=2840msec, maxt=2955msec - WRITE: io=64MB, aggrb=1302, minb=666, maxb=669, mint=50093msec, maxt=50320msec - -For each data direction, it prints: - -**io** - Number of megabytes I/O performed. -**aggrb** - Aggregate bandwidth of threads in this group. -**minb** - The minimum average bandwidth a thread saw. -**maxb** - The maximum average bandwidth a thread saw. -**mint** - The smallest runtime of the threads in that group. -**maxt** - The longest runtime of the threads in that group. - -And finally, the disk statistics are printed. They will look like this:: - - Disk stats (read/write): - sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00% - -Each value is printed for both reads and writes, with reads first. The -numbers denote: - -**ios** - Number of I/Os performed by all groups. -**merge** - Number of merges I/O the I/O scheduler. -**ticks** - Number of ticks we kept the disk busy. -**io_queue** - Total time spent in the disk queue. -**util** - The disk utilization. A value of 100% means we kept the disk - busy constantly, 50% would be a disk idling half of the time. - -It is also possible to get fio to dump the current output while it is running, -without terminating the job. To do that, send fio the **USR1** signal. You can -also get regularly timed dumps by using the :option:`--status-interval` -parameter, or by creating a file in :file:`/tmp` named -:file:`fio-dump-status`. If fio sees this file, it will unlink it and dump the -current output status. - - -Terse output ------------- - -For scripted usage where you typically want to generate tables or graphs of the -results, fio can output the results in a semicolon separated format. The format -is one long line of values, such as:: - - 2;card0;0;0;7139336;121836;60004;1;10109;27.932460;116.933948;220;126861;3495.446807;1085.368601;226;126864;3523.635629;1089.012448;24063;99944;50.275485%;59818.274627;5540.657370;7155060;122104;60004;1;8338;29.086342;117.839068;388;128077;5032.488518;1234.785715;391;128085;5061.839412;1236.909129;23436;100928;50.287926%;59964.832030;5644.844189;14.595833%;19.394167%;123706;0;7313;0.1%;0.1%;0.1%;0.1%;0.1%;0.1%;100.0%;0.00%;0.00%;0.00%;0.00%;0.00%;0.00%;0.01%;0.02%;0.05%;0.16%;6.04%;40.40%;52.68%;0.64%;0.01%;0.00%;0.01%;0.00%;0.00%;0.00%;0.00%;0.00% - A description of this job goes here. - -The job description (if provided) follows on a second line. - -To enable terse output, use the :option:`--minimal` command line option. The -first value is the version of the terse output format. If the output has to be -changed for some reason, this number will be incremented by 1 to signify that -change. - -Split up, the format is as follows: - - :: - - terse version, fio version, jobname, groupid, error - - READ status:: - - Total IO (KiB), bandwidth (KiB/sec), IOPS, runtime (msec) - Submission latency: min, max, mean, stdev (usec) - Completion latency: min, max, mean, stdev (usec) - Completion latency percentiles: 20 fields (see below) - Total latency: min, max, mean, stdev (usec) - Bw (KiB/s): min, max, aggregate percentage of total, mean, stdev - - WRITE status: - - :: - - Total IO (KiB), bandwidth (KiB/sec), IOPS, runtime (msec) - Submission latency: min, max, mean, stdev (usec) - Completion latency: min, max, mean, stdev(usec) - Completion latency percentiles: 20 fields (see below) - Total latency: min, max, mean, stdev (usec) - Bw (KiB/s): min, max, aggregate percentage of total, mean, stdev - - CPU usage:: - - user, system, context switches, major faults, minor faults - - I/O depths:: - - <=1, 2, 4, 8, 16, 32, >=64 - - I/O latencies microseconds:: - - <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000 - - I/O latencies milliseconds:: - - <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, 2000, >=2000 - - Disk utilization:: - - Disk name, Read ios, write ios, - Read merges, write merges, - Read ticks, write ticks, - Time spent in queue, disk utilization percentage - - Additional Info (dependent on continue_on_error, default off):: - - total # errors, first error code - - Additional Info (dependent on description being set):: - - Text description - -Completion latency percentiles can be a grouping of up to 20 sets, so for the -terse output fio writes all of them. Each field will look like this:: - - 1.00%=6112 - -which is the Xth percentile, and the `usec` latency associated with it. - -For disk utilization, all disks used by fio are shown. So for each disk there -will be a disk utilization section. - - -Trace file format ------------------ - -There are two trace file format that you can encounter. The older (v1) format is -unsupported since version 1.20-rc3 (March 2008). It will still be described -below in case that you get an old trace and want to understand it. - -In any case the trace is a simple text file with a single action per line. - - -Trace file format v1 -~~~~~~~~~~~~~~~~~~~~ - -Each line represents a single I/O action in the following format:: - - rw, offset, length - -where `rw=0/1` for read/write, and the offset and length entries being in bytes. - -This format is not supported in fio versions => 1.20-rc3. - - -Trace file format v2 -~~~~~~~~~~~~~~~~~~~~ - -The second version of the trace file format was added in fio version 1.17. It -allows to access more then one file per trace and has a bigger set of possible -file actions. - -The first line of the trace file has to be:: - - fio version 2 iolog - -Following this can be lines in two different formats, which are described below. - -The file management format:: - - filename action - -The filename is given as an absolute path. The action can be one of these: - -**add** - Add the given filename to the trace. -**open** - Open the file with the given filename. The filename has to have - been added with the **add** action before. -**close** - Close the file with the given filename. The file has to have been - opened before. - - -The file I/O action format:: - - filename action offset length - -The `filename` is given as an absolute path, and has to have been added and -opened before it can be used with this format. The `offset` and `length` are -given in bytes. The `action` can be one of these: - -**wait** - Wait for `offset` microseconds. Everything below 100 is discarded. - The time is relative to the previous `wait` statement. -**read** - Read `length` bytes beginning from `offset`. -**write** - Write `length` bytes beginning from `offset`. -**sync** - :manpage:`fsync(2)` the file. -**datasync** - :manpage:`fdatasync(2)` the file. -**trim** - Trim the given file from the given `offset` for `length` bytes. - -CPU idleness profiling ----------------------- - -In some cases, we want to understand CPU overhead in a test. For example, we -test patches for the specific goodness of whether they reduce CPU usage. -Fio implements a balloon approach to create a thread per CPU that runs at idle -priority, meaning that it only runs when nobody else needs the cpu. -By measuring the amount of work completed by the thread, idleness of each CPU -can be derived accordingly. - -An unit work is defined as touching a full page of unsigned characters. Mean and -standard deviation of time to complete an unit work is reported in "unit work" -section. Options can be chosen to report detailed percpu idleness or overall -system idleness by aggregating percpu stats. - - -Verification and triggers -------------------------- - -Fio is usually run in one of two ways, when data verification is done. The first -is a normal write job of some sort with verify enabled. When the write phase has -completed, fio switches to reads and verifies everything it wrote. The second -model is running just the write phase, and then later on running the same job -(but with reads instead of writes) to repeat the same I/O patterns and verify -the contents. Both of these methods depend on the write phase being completed, -as fio otherwise has no idea how much data was written. - -With verification triggers, fio supports dumping the current write state to -local files. Then a subsequent read verify workload can load this state and know -exactly where to stop. This is useful for testing cases where power is cut to a -server in a managed fashion, for instance. - -A verification trigger consists of two things: - -1) Storing the write state of each job. -2) Executing a trigger command. - -The write state is relatively small, on the order of hundreds of bytes to single -kilobytes. It contains information on the number of completions done, the last X -completions, etc. - -A trigger is invoked either through creation ('touch') of a specified file in -the system, or through a timeout setting. If fio is run with -:option:`--trigger-file` = :file:`/tmp/trigger-file`, then it will continually -check for the existence of :file:`/tmp/trigger-file`. When it sees this file, it -will fire off the trigger (thus saving state, and executing the trigger -command). - -For client/server runs, there's both a local and remote trigger. If fio is -running as a server backend, it will send the job states back to the client for -safe storage, then execute the remote trigger, if specified. If a local trigger -is specified, the server will still send back the write state, but the client -will then execute the trigger. - -Verification trigger example -~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -Lets say we want to run a powercut test on the remote machine 'server'. Our -write workload is in :file:`write-test.fio`. We want to cut power to 'server' at -some point during the run, and we'll run this test from the safety or our local -machine, 'localbox'. On the server, we'll start the fio backend normally:: - - server# fio --server - -and on the client, we'll fire off the workload:: - - localbox$ fio --client=server --trigger-file=/tmp/my-trigger --trigger-remote="bash -c \"echo b > /proc/sysrq-triger\"" - -We set :file:`/tmp/my-trigger` as the trigger file, and we tell fio to execute:: - - echo b > /proc/sysrq-trigger - -on the server once it has received the trigger and sent us the write state. This -will work, but it's not **really** cutting power to the server, it's merely -abruptly rebooting it. If we have a remote way of cutting power to the server -through IPMI or similar, we could do that through a local trigger command -instead. Lets assume we have a script that does IPMI reboot of a given hostname, -ipmi-reboot. On localbox, we could then have run fio with a local trigger -instead:: - - localbox$ fio --client=server --trigger-file=/tmp/my-trigger --trigger="ipmi-reboot server" - -For this case, fio would wait for the server to send us the write state, then -execute ``ipmi-reboot server`` when that happened. - -Loading verify state -~~~~~~~~~~~~~~~~~~~~ - -To load store write state, read verification job file must contain the -:option:`verify_state_load` option. If that is set, fio will load the previously -stored state. For a local fio run this is done by loading the files directly, -and on a client/server run, the server backend will ask the client to send the -files over and load them from there. - - -Log File Formats ----------------- - -Fio supports a variety of log file formats, for logging latencies, bandwidth, -and IOPS. The logs share a common format, which looks like this: - - *time* (`msec`), *value*, *data direction*, *offset* - -Time for the log entry is always in milliseconds. The *value* logged depends -on the type of log, it will be one of the following: - - **Latency log** - Value is latency in usecs - **Bandwidth log** - Value is in KiB/sec - **IOPS log** - Value is IOPS - -*Data direction* is one of the following: - - **0** - I/O is a READ - **1** - I/O is a WRITE - **2** - I/O is a TRIM - -The *offset* is the offset, in bytes, from the start of the file, for that -particular I/O. The logging of the offset can be toggled with -:option:`log_offset`. - -If windowed logging is enabled through :option:`log_avg_msec` then fio doesn't -log individual I/Os. Instead of logs the average values over the specified period -of time. Since 'data direction' and 'offset' are per-I/O values, they aren't -applicable if windowed logging is enabled. If windowed logging is enabled and -:option:`log_max_value` is set, then fio logs maximum values in that window -instead of averages. - - -Client/server -------------- - -Normally fio is invoked as a stand-alone application on the machine where the -I/O workload should be generated. However, the frontend and backend of fio can -be run separately. Ie the fio server can generate an I/O workload on the "Device -Under Test" while being controlled from another machine. - -Start the server on the machine which has access to the storage DUT:: - - fio --server=args - -where args defines what fio listens to. The arguments are of the form -``type,hostname`` or ``IP,port``. *type* is either ``ip`` (or ip4) for TCP/IP -v4, ``ip6`` for TCP/IP v6, or ``sock`` for a local unix domain socket. -*hostname* is either a hostname or IP address, and *port* is the port to listen -to (only valid for TCP/IP, not a local socket). Some examples: - -1) ``fio --server`` - - Start a fio server, listening on all interfaces on the default port (8765). - -2) ``fio --server=ip:hostname,4444`` - - Start a fio server, listening on IP belonging to hostname and on port 4444. - -3) ``fio --server=ip6:::1,4444`` - - Start a fio server, listening on IPv6 localhost ::1 and on port 4444. - -4) ``fio --server=,4444`` - - Start a fio server, listening on all interfaces on port 4444. - -5) ``fio --server=1.2.3.4`` - - Start a fio server, listening on IP 1.2.3.4 on the default port. - -6) ``fio --server=sock:/tmp/fio.sock`` - - Start a fio server, listening on the local socket /tmp/fio.sock. - -Once a server is running, a "client" can connect to the fio server with:: - - fio <local-args> --client=<server> <remote-args> <job file(s)> - -where `local-args` are arguments for the client where it is running, `server` -is the connect string, and `remote-args` and `job file(s)` are sent to the -server. The `server` string follows the same format as it does on the server -side, to allow IP/hostname/socket and port strings. - -Fio can connect to multiple servers this way:: - - fio --client=<server1> <job file(s)> --client=<server2> <job file(s)> - -If the job file is located on the fio server, then you can tell the server to -load a local file as well. This is done by using :option:`--remote-config` :: - - fio --client=server --remote-config /path/to/file.fio - -Then fio will open this local (to the server) job file instead of being passed -one from the client. - -If you have many servers (example: 100 VMs/containers), you can input a pathname -of a file containing host IPs/names as the parameter value for the -:option:`--client` option. For example, here is an example :file:`host.list` -file containing 2 hostnames:: - - host1.your.dns.domain - host2.your.dns.domain - -The fio command would then be:: - - fio --client=host.list <job file(s)> - -In this mode, you cannot input server-specific parameters or job files -- all -servers receive the same job file. - -In order to let ``fio --client`` runs use a shared filesystem from multiple -hosts, ``fio --client`` now prepends the IP address of the server to the -filename. For example, if fio is using directory :file:`/mnt/nfs/fio` and is -writing filename :file:`fileio.tmp`, with a :option:`--client` `hostfile` -containing two hostnames ``h1`` and ``h2`` with IP addresses 192.168.10.120 and -192.168.10.121, then fio will create two files:: - - /mnt/nfs/fio/192.168.10.120.fileio.tmp - /mnt/nfs/fio/192.168.10.121.fileio.tmp |