4 The first step in getting fio to simulate a desired I/O workload, is writing a
5 job file describing that specific setup. A job file may contain any number of
6 threads and/or files -- the typical contents of the job file is a *global*
7 section defining shared parameters, and one or more job sections describing the
8 jobs involved. When run, fio parses this file and sets everything up as
9 described. If we break down a job from top to bottom, it contains the following
14 Defines the I/O pattern issued to the file(s). We may only be reading
15 sequentially from this file(s), or we may be writing randomly. Or even
16 mixing reads and writes, sequentially or randomly.
17 Should we be doing buffered I/O, or direct/raw I/O?
21 In how large chunks are we issuing I/O? This may be a single value,
22 or it may describe a range of block sizes.
26 How much data are we going to be reading/writing.
30 How do we issue I/O? We could be memory mapping the file, we could be
31 using regular read/write, we could be using splice, async I/O, or even
36 If the I/O engine is async, how large a queuing depth do we want to
42 How many files are we spreading the workload over.
44 `Threads, processes and job synchronization`_
46 How many threads or processes should we spread this workload over.
48 The above are the basic parameters defined for a workload, in addition there's a
49 multitude of parameters that modify other aspects of how this job behaves.
55 .. option:: --debug=type
57 Enable verbose tracing `type` of various fio actions. May be ``all`` for all types
58 or individual types separated by a comma (e.g. ``--debug=file,mem`` will
59 enable file and memory debugging). Currently, additional logging is
63 Dump info related to processes.
65 Dump info related to file actions.
67 Dump info related to I/O queuing.
69 Dump info related to memory allocations.
71 Dump info related to blktrace setup.
73 Dump info related to I/O verification.
75 Enable all debug options.
77 Dump info related to random offset generation.
79 Dump info related to option matching and parsing.
81 Dump info related to disk utilization updates.
83 Dump info only related to job number x.
85 Dump info only related to mutex up/down ops.
87 Dump info related to profile extensions.
89 Dump info related to internal time keeping.
91 Dump info related to networking connections.
93 Dump info related to I/O rate switching.
95 Dump info related to log compress/decompress.
97 Dump info related to steadystate detection.
99 Dump info related to the helper thread.
101 Dump info related to support for zoned block devices.
103 Show available debug options.
105 .. option:: --parse-only
107 Parse options only, don't start any I/O.
109 .. option:: --merge-blktrace-only
111 Merge blktraces only, don't start any I/O.
113 .. option:: --output=filename
115 Write output to file `filename`.
117 .. option:: --output-format=format
119 Set the reporting `format` to `normal`, `terse`, `json`, or `json+`. Multiple
120 formats can be selected, separated by a comma. `terse` is a CSV based
121 format. `json+` is like `json`, except it adds a full dump of the latency
124 .. option:: --bandwidth-log
126 Generate aggregate bandwidth logs.
128 .. option:: --minimal
130 Print statistics in a terse, semicolon-delimited format.
132 .. option:: --append-terse
134 Print statistics in selected mode AND terse, semicolon-delimited format.
135 **Deprecated**, use :option:`--output-format` instead to select multiple
138 .. option:: --terse-version=version
140 Set terse `version` output format (default 3, or 2 or 4 or 5).
142 .. option:: --version
144 Print version information and exit.
148 Print a summary of the command line options and exit.
150 .. option:: --cpuclock-test
152 Perform test and validation of internal CPU clock.
154 .. option:: --crctest=[test]
156 Test the speed of the built-in checksumming functions. If no argument is
157 given, all of them are tested. Alternatively, a comma separated list can
158 be passed, in which case the given ones are tested.
160 .. option:: --cmdhelp=command
162 Print help information for `command`. May be ``all`` for all commands.
164 .. option:: --enghelp=[ioengine[,command]]
166 List all commands defined by `ioengine`, or print help for `command`
167 defined by `ioengine`. If no `ioengine` is given, list all
170 .. option:: --showcmd
172 Convert given job files to a set of command-line options.
174 .. option:: --readonly
176 Turn on safety read-only checks, preventing writes and trims. The
177 ``--readonly`` option is an extra safety guard to prevent users from
178 accidentally starting a write or trim workload when that is not desired.
179 Fio will only modify the device under test if
180 `rw=write/randwrite/rw/randrw/trim/randtrim/trimwrite` is given. This
181 safety net can be used as an extra precaution.
183 .. option:: --eta=when
185 Specifies when real-time ETA estimate should be printed. `when` may be
186 `always`, `never` or `auto`. `auto` is the default, it prints ETA
187 when requested if the output is a TTY. `always` disregards the output
188 type, and prints ETA when requested. `never` never prints ETA.
190 .. option:: --eta-interval=time
192 By default, fio requests client ETA status roughly every second. With
193 this option, the interval is configurable. Fio imposes a minimum
194 allowed time to avoid flooding the console, less than 250 msec is
197 .. option:: --eta-newline=time
199 Force a new line for every `time` period passed. When the unit is omitted,
200 the value is interpreted in seconds.
202 .. option:: --status-interval=time
204 Force a full status dump of cumulative (from job start) values at `time`
205 intervals. This option does *not* provide per-period measurements. So
206 values such as bandwidth are running averages. When the time unit is omitted,
207 `time` is interpreted in seconds. Note that using this option with
208 ``--output-format=json`` will yield output that technically isn't valid
209 json, since the output will be collated sets of valid json. It will need
210 to be split into valid sets of json after the run.
212 .. option:: --section=name
214 Only run specified section `name` in job file. Multiple sections can be specified.
215 The ``--section`` option allows one to combine related jobs into one file.
216 E.g. one job file could define light, moderate, and heavy sections. Tell
217 fio to run only the "heavy" section by giving ``--section=heavy``
218 command line option. One can also specify the "write" operations in one
219 section and "verify" operation in another section. The ``--section`` option
220 only applies to job sections. The reserved *global* section is always
223 .. option:: --alloc-size=kb
225 Allocate additional internal smalloc pools of size `kb` in KiB. The
226 ``--alloc-size`` option increases shared memory set aside for use by fio.
227 If running large jobs with randommap enabled, fio can run out of memory.
228 Smalloc is an internal allocator for shared structures from a fixed size
229 memory pool and can grow to 16 pools. The pool size defaults to 16MiB.
231 NOTE: While running :file:`.fio_smalloc.*` backing store files are visible
234 .. option:: --warnings-fatal
236 All fio parser warnings are fatal, causing fio to exit with an
239 .. option:: --max-jobs=nr
241 Set the maximum number of threads/processes to support to `nr`.
242 NOTE: On Linux, it may be necessary to increase the shared-memory
243 limit (:file:`/proc/sys/kernel/shmmax`) if fio runs into errors while
246 .. option:: --server=args
248 Start a backend server, with `args` specifying what to listen to.
249 See `Client/Server`_ section.
251 .. option:: --daemonize=pidfile
253 Background a fio server, writing the pid to the given `pidfile` file.
255 .. option:: --client=hostname
257 Instead of running the jobs locally, send and run them on the given `hostname`
258 or set of `hostname`\s. See `Client/Server`_ section.
260 .. option:: --remote-config=file
262 Tell fio server to load this local `file`.
264 .. option:: --idle-prof=option
266 Report CPU idleness. `option` is one of the following:
269 Run unit work calibration only and exit.
272 Show aggregate system idleness and unit work.
275 As **system** but also show per CPU idleness.
277 .. option:: --inflate-log=log
279 Inflate and output compressed `log`.
281 .. option:: --trigger-file=file
283 Execute trigger command when `file` exists.
285 .. option:: --trigger-timeout=time
287 Execute trigger at this `time`.
289 .. option:: --trigger=command
291 Set this `command` as local trigger.
293 .. option:: --trigger-remote=command
295 Set this `command` as remote trigger.
297 .. option:: --aux-path=path
299 Use the directory specified by `path` for generated state files instead
300 of the current working directory.
302 Any parameters following the options will be assumed to be job files, unless
303 they match a job file parameter. Multiple job files can be listed and each job
304 file will be regarded as a separate group. Fio will :option:`stonewall`
305 execution between each group.
311 As previously described, fio accepts one or more job files describing what it is
312 supposed to do. The job file format is the classic ini file, where the names
313 enclosed in [] brackets define the job name. You are free to use any ASCII name
314 you want, except *global* which has special meaning. Following the job name is
315 a sequence of zero or more parameters, one per line, that define the behavior of
316 the job. If the first character in a line is a ';' or a '#', the entire line is
317 discarded as a comment.
319 A *global* section sets defaults for the jobs described in that file. A job may
320 override a *global* section parameter, and a job file may even have several
321 *global* sections if so desired. A job is only affected by a *global* section
324 The :option:`--cmdhelp` option also lists all options. If used with a `command`
325 argument, :option:`--cmdhelp` will detail the given `command`.
327 See the `examples/` directory for inspiration on how to write job files. Note
328 the copyright and license requirements currently apply to `examples/` files.
330 So let's look at a really simple job file that defines two processes, each
331 randomly reading from a 128MiB file:
335 ; -- start job file --
346 As you can see, the job file sections themselves are empty as all the described
347 parameters are shared. As no :option:`filename` option is given, fio makes up a
348 `filename` for each of the jobs as it sees fit. On the command line, this job
349 would look as follows::
351 $ fio --name=global --rw=randread --size=128m --name=job1 --name=job2
354 Let's look at an example that has a number of processes writing randomly to
359 ; -- start job file --
370 Here we have no *global* section, as we only have one job defined anyway. We
371 want to use async I/O here, with a depth of 4 for each file. We also increased
372 the buffer size used to 32KiB and define numjobs to 4 to fork 4 identical
373 jobs. The result is 4 processes each randomly writing to their own 64MiB
374 file. Instead of using the above job file, you could have given the parameters
375 on the command line. For this case, you would specify::
377 $ fio --name=random-writers --ioengine=libaio --iodepth=4 --rw=randwrite --bs=32k --direct=0 --size=64m --numjobs=4
379 When fio is utilized as a basis of any reasonably large test suite, it might be
380 desirable to share a set of standardized settings across multiple job files.
381 Instead of copy/pasting such settings, any section may pull in an external
382 :file:`filename.fio` file with *include filename* directive, as in the following
385 ; -- start job file including.fio --
389 include glob-include.fio
396 include test-include.fio
397 ; -- end job file including.fio --
401 ; -- start job file glob-include.fio --
404 ; -- end job file glob-include.fio --
408 ; -- start job file test-include.fio --
411 ; -- end job file test-include.fio --
413 Settings pulled into a section apply to that section only (except *global*
414 section). Include directives may be nested in that any included file may contain
415 further include directive(s). Include files may not contain [] sections.
418 Environment variables
419 ~~~~~~~~~~~~~~~~~~~~~
421 Fio also supports environment variable expansion in job files. Any sub-string of
422 the form ``${VARNAME}`` as part of an option value (in other words, on the right
423 of the '='), will be expanded to the value of the environment variable called
424 `VARNAME`. If no such environment variable is defined, or `VARNAME` is the
425 empty string, the empty string will be substituted.
427 As an example, let's look at a sample fio invocation and job file::
429 $ SIZE=64m NUMJOBS=4 fio jobfile.fio
433 ; -- start job file --
440 This will expand to the following equivalent job file at runtime:
444 ; -- start job file --
451 Fio ships with a few example job files, you can also look there for inspiration.
456 Additionally, fio has a set of reserved keywords that will be replaced
457 internally with the appropriate value. Those keywords are:
461 The architecture page size of the running system.
465 Megabytes of total memory in the system.
469 Number of online available CPUs.
471 These can be used on the command line or in the job file, and will be
472 automatically substituted with the current system values when the job is
473 run. Simple math is also supported on these keywords, so you can perform actions
478 and get that properly expanded to 8 times the size of memory in the machine.
484 This section describes in details each parameter associated with a job. Some
485 parameters take an option of a given type, such as an integer or a
486 string. Anywhere a numeric value is required, an arithmetic expression may be
487 used, provided it is surrounded by parentheses. Supported operators are:
496 For time values in expressions, units are microseconds by default. This is
497 different than for time values not in expressions (not enclosed in
498 parentheses). The following types are used:
505 String: A sequence of alphanumeric characters.
508 Integer with possible time suffix. Without a unit value is interpreted as
509 seconds unless otherwise specified. Accepts a suffix of 'd' for days, 'h' for
510 hours, 'm' for minutes, 's' for seconds, 'ms' (or 'msec') for milliseconds and
511 'us' (or 'usec') for microseconds. For example, use 10m for 10 minutes.
516 Integer. A whole number value, which may contain an integer prefix
517 and an integer suffix:
519 [*integer prefix*] **number** [*integer suffix*]
521 The optional *integer prefix* specifies the number's base. The default
522 is decimal. *0x* specifies hexadecimal.
524 The optional *integer suffix* specifies the number's units, and includes an
525 optional unit prefix and an optional unit. For quantities of data, the
526 default unit is bytes. For quantities of time, the default unit is seconds
527 unless otherwise specified.
529 With :option:`kb_base`\=1000, fio follows international standards for unit
530 prefixes. To specify power-of-10 decimal values defined in the
531 International System of Units (SI):
533 * *K* -- means kilo (K) or 1000
534 * *M* -- means mega (M) or 1000**2
535 * *G* -- means giga (G) or 1000**3
536 * *T* -- means tera (T) or 1000**4
537 * *P* -- means peta (P) or 1000**5
539 To specify power-of-2 binary values defined in IEC 80000-13:
541 * *Ki* -- means kibi (Ki) or 1024
542 * *Mi* -- means mebi (Mi) or 1024**2
543 * *Gi* -- means gibi (Gi) or 1024**3
544 * *Ti* -- means tebi (Ti) or 1024**4
545 * *Pi* -- means pebi (Pi) or 1024**5
547 For Zone Block Device Mode:
550 With :option:`kb_base`\=1024 (the default), the unit prefixes are opposite
551 from those specified in the SI and IEC 80000-13 standards to provide
552 compatibility with old scripts. For example, 4k means 4096.
554 For quantities of data, an optional unit of 'B' may be included
555 (e.g., 'kB' is the same as 'k').
557 The *integer suffix* is not case sensitive (e.g., m/mi mean mebi/mega,
558 not milli). 'b' and 'B' both mean byte, not bit.
560 Examples with :option:`kb_base`\=1000:
562 * *4 KiB*: 4096, 4096b, 4096B, 4ki, 4kib, 4kiB, 4Ki, 4KiB
563 * *1 MiB*: 1048576, 1mi, 1024ki
564 * *1 MB*: 1000000, 1m, 1000k
565 * *1 TiB*: 1099511627776, 1ti, 1024gi, 1048576mi
566 * *1 TB*: 1000000000, 1t, 1000m, 1000000k
568 Examples with :option:`kb_base`\=1024 (default):
570 * *4 KiB*: 4096, 4096b, 4096B, 4k, 4kb, 4kB, 4K, 4KB
571 * *1 MiB*: 1048576, 1m, 1024k
572 * *1 MB*: 1000000, 1mi, 1000ki
573 * *1 TiB*: 1099511627776, 1t, 1024g, 1048576m
574 * *1 TB*: 1000000000, 1ti, 1000mi, 1000000ki
576 To specify times (units are not case sensitive):
580 * *M* -- means minutes
581 * *s* -- or sec means seconds (default)
582 * *ms* -- or *msec* means milliseconds
583 * *us* -- or *usec* means microseconds
585 If the option accepts an upper and lower range, use a colon ':' or
586 minus '-' to separate such values. See :ref:`irange <irange>`.
587 If the lower value specified happens to be larger than the upper value
588 the two values are swapped.
593 Boolean. Usually parsed as an integer, however only defined for
594 true and false (1 and 0).
599 Integer range with suffix. Allows value range to be given, such as
600 1024-4096. A colon may also be used as the separator, e.g. 1k:4k. If the
601 option allows two sets of ranges, they can be specified with a ',' or '/'
602 delimiter: 1k-4k/8k-32k. Also see :ref:`int <int>`.
605 A list of floating point numbers, separated by a ':' character.
607 With the above in mind, here follows the complete list of fio job parameters.
613 .. option:: kb_base=int
615 Select the interpretation of unit prefixes in input parameters.
618 Inputs comply with IEC 80000-13 and the International
619 System of Units (SI). Use:
621 - power-of-2 values with IEC prefixes (e.g., KiB)
622 - power-of-10 values with SI prefixes (e.g., kB)
625 Compatibility mode (default). To avoid breaking old scripts:
627 - power-of-2 values with SI prefixes
628 - power-of-10 values with IEC prefixes
630 See :option:`bs` for more details on input parameters.
632 Outputs always use correct prefixes. Most outputs include both
635 bw=2383.3kB/s (2327.4KiB/s)
637 If only one value is reported, then kb_base selects the one to use:
639 **1000** -- SI prefixes
641 **1024** -- IEC prefixes
643 .. option:: unit_base=int
645 Base unit for reporting. Allowed values are:
648 Use auto-detection (default).
660 ASCII name of the job. This may be used to override the name printed by fio
661 for this job. Otherwise the job name is used. On the command line this
662 parameter has the special purpose of also signaling the start of a new job.
664 .. option:: description=str
666 Text description of the job. Doesn't do anything except dump this text
667 description when this job is run. It's not parsed.
669 .. option:: loops=int
671 Run the specified number of iterations of this job. Used to repeat the same
672 workload a given number of times. Defaults to 1.
674 .. option:: numjobs=int
676 Create the specified number of clones of this job. Each clone of job
677 is spawned as an independent thread or process. May be used to setup a
678 larger number of threads/processes doing the same thing. Each thread is
679 reported separately; to see statistics for all clones as a whole, use
680 :option:`group_reporting` in conjunction with :option:`new_group`.
681 See :option:`--max-jobs`. Default: 1.
684 Time related parameters
685 ~~~~~~~~~~~~~~~~~~~~~~~
687 .. option:: runtime=time
689 Limit runtime. The test will run until it completes the configured I/O
690 workload or until it has run for this specified amount of time, whichever
691 occurs first. It can be quite hard to determine for how long a specified
692 job will run, so this parameter is handy to cap the total runtime to a
693 given time. When the unit is omitted, the value is interpreted in
696 .. option:: time_based
698 If set, fio will run for the duration of the :option:`runtime` specified
699 even if the file(s) are completely read or written. It will simply loop over
700 the same workload as many times as the :option:`runtime` allows.
702 .. option:: startdelay=irange(time)
704 Delay the start of job for the specified amount of time. Can be a single
705 value or a range. When given as a range, each thread will choose a value
706 randomly from within the range. Value is in seconds if a unit is omitted.
708 .. option:: ramp_time=time
710 If set, fio will run the specified workload for this amount of time before
711 logging any performance numbers. Useful for letting performance settle
712 before logging results, thus minimizing the runtime required for stable
713 results. Note that the ``ramp_time`` is considered lead in time for a job,
714 thus it will increase the total runtime if a special timeout or
715 :option:`runtime` is specified. When the unit is omitted, the value is
718 .. option:: clocksource=str
720 Use the given clocksource as the base of timing. The supported options are:
723 :manpage:`gettimeofday(2)`
726 :manpage:`clock_gettime(2)`
729 Internal CPU clock source
731 cpu is the preferred clocksource if it is reliable, as it is very fast (and
732 fio is heavy on time calls). Fio will automatically use this clocksource if
733 it's supported and considered reliable on the system it is running on,
734 unless another clocksource is specifically set. For x86/x86-64 CPUs, this
735 means supporting TSC Invariant.
737 .. option:: gtod_reduce=bool
739 Enable all of the :manpage:`gettimeofday(2)` reducing options
740 (:option:`disable_clat`, :option:`disable_slat`, :option:`disable_bw_measurement`) plus
741 reduce precision of the timeout somewhat to really shrink the
742 :manpage:`gettimeofday(2)` call count. With this option enabled, we only do
743 about 0.4% of the :manpage:`gettimeofday(2)` calls we would have done if all
744 time keeping was enabled.
746 .. option:: gtod_cpu=int
748 Sometimes it's cheaper to dedicate a single thread of execution to just
749 getting the current time. Fio (and databases, for instance) are very
750 intensive on :manpage:`gettimeofday(2)` calls. With this option, you can set
751 one CPU aside for doing nothing but logging current time to a shared memory
752 location. Then the other threads/processes that run I/O workloads need only
753 copy that segment, instead of entering the kernel with a
754 :manpage:`gettimeofday(2)` call. The CPU set aside for doing these time
755 calls will be excluded from other uses. Fio will manually clear it from the
756 CPU mask of other jobs.
758 .. option:: job_start_clock_id=int
759 The clock_id passed to the call to `clock_gettime` used to record job_start
760 in the `json` output format. Default is 0, or CLOCK_REALTIME.
766 .. option:: directory=str
768 Prefix filenames with this directory. Used to place files in a different
769 location than :file:`./`. You can specify a number of directories by
770 separating the names with a ':' character. These directories will be
771 assigned equally distributed to job clones created by :option:`numjobs` as
772 long as they are using generated filenames. If specific `filename(s)` are
773 set fio will use the first listed directory, and thereby matching the
774 `filename` semantic (which generates a file for each clone if not
775 specified, but lets all clones use the same file if set).
777 See the :option:`filename` option for information on how to escape "``:``"
778 characters within the directory path itself.
780 Note: To control the directory fio will use for internal state files
781 use :option:`--aux-path`.
783 .. option:: filename=str
785 Fio normally makes up a `filename` based on the job name, thread number, and
786 file number (see :option:`filename_format`). If you want to share files
787 between threads in a job or several
788 jobs with fixed file paths, specify a `filename` for each of them to override
789 the default. If the ioengine is file based, you can specify a number of files
790 by separating the names with a ':' colon. So if you wanted a job to open
791 :file:`/dev/sda` and :file:`/dev/sdb` as the two working files, you would use
792 ``filename=/dev/sda:/dev/sdb``. This also means that whenever this option is
793 specified, :option:`nrfiles` is ignored. The size of regular files specified
794 by this option will be :option:`size` divided by number of files unless an
795 explicit size is specified by :option:`filesize`.
797 Each colon in the wanted path must be escaped with a ``\``
798 character. For instance, if the path is :file:`/dev/dsk/foo@3,0:c` then you
799 would use ``filename=/dev/dsk/foo@3,0\:c`` and if the path is
800 :file:`F:\\filename` then you would use ``filename=F\:\filename``.
802 On Windows, disk devices are accessed as :file:`\\\\.\\PhysicalDrive0` for
803 the first device, :file:`\\\\.\\PhysicalDrive1` for the second etc.
804 Note: Windows and FreeBSD prevent write access to areas
805 of the disk containing in-use data (e.g. filesystems).
807 The filename "`-`" is a reserved name, meaning *stdin* or *stdout*. Which
808 of the two depends on the read/write direction set.
810 .. option:: filename_format=str
812 If sharing multiple files between jobs, it is usually necessary to have fio
813 generate the exact names that you want. By default, fio will name a file
814 based on the default file format specification of
815 :file:`jobname.jobnumber.filenumber`. With this option, that can be
816 customized. Fio will recognize and replace the following keywords in this
820 The name of the worker thread or process.
822 IP of the fio process when using client/server mode.
824 The incremental number of the worker thread or process.
826 The incremental number of the file for that worker thread or
829 To have dependent jobs share a set of files, this option can be set to have
830 fio generate filenames that are shared between the two. For instance, if
831 :file:`testfiles.$filenum` is specified, file number 4 for any job will be
832 named :file:`testfiles.4`. The default of :file:`$jobname.$jobnum.$filenum`
833 will be used if no other format specifier is given.
835 If you specify a path then the directories will be created up to the
836 main directory for the file. So for example if you specify
837 ``filename_format=a/b/c/$jobnum`` then the directories a/b/c will be
838 created before the file setup part of the job. If you specify
839 :option:`directory` then the path will be relative that directory,
840 otherwise it is treated as the absolute path.
842 .. option:: unique_filename=bool
844 To avoid collisions between networked clients, fio defaults to prefixing any
845 generated filenames (with a directory specified) with the source of the
846 client connecting. To disable this behavior, set this option to 0.
848 .. option:: opendir=str
850 Recursively open any files below directory `str`. This accepts only a
851 single directory and unlike related options, colons appearing in the
852 path must not be escaped.
854 .. option:: lockfile=str
856 Fio defaults to not locking any files before it does I/O to them. If a file
857 or file descriptor is shared, fio can serialize I/O to that file to make the
858 end result consistent. This is usual for emulating real workloads that share
859 files. The lock modes are:
862 No locking. The default.
864 Only one thread or process may do I/O at a time, excluding all
867 Read-write locking on the file. Many readers may
868 access the file at the same time, but writes get exclusive access.
870 .. option:: nrfiles=int
872 Number of files to use for this job. Defaults to 1. The size of files
873 will be :option:`size` divided by this unless explicit size is specified by
874 :option:`filesize`. Files are created for each thread separately, and each
875 file will have a file number within its name by default, as explained in
876 :option:`filename` section.
879 .. option:: openfiles=int
881 Number of files to keep open at the same time. Defaults to the same as
882 :option:`nrfiles`, can be set smaller to limit the number simultaneous
885 .. option:: file_service_type=str
887 Defines how fio decides which file from a job to service next. The following
891 Choose a file at random.
894 Round robin over opened files. This is the default.
897 Finish one file before moving on to the next. Multiple files can
898 still be open depending on :option:`openfiles`.
901 Use a *Zipf* distribution to decide what file to access.
904 Use a *Pareto* distribution to decide what file to access.
907 Use a *Gaussian* (normal) distribution to decide what file to
913 For *random*, *roundrobin*, and *sequential*, a postfix can be appended to
914 tell fio how many I/Os to issue before switching to a new file. For example,
915 specifying ``file_service_type=random:8`` would cause fio to issue
916 8 I/Os before selecting a new file at random. For the non-uniform
917 distributions, a floating point postfix can be given to influence how the
918 distribution is skewed. See :option:`random_distribution` for a description
919 of how that would work.
921 .. option:: ioscheduler=str
923 Attempt to switch the device hosting the file to the specified I/O scheduler
926 .. option:: create_serialize=bool
928 If true, serialize the file creation for the jobs. This may be handy to
929 avoid interleaving of data files, which may greatly depend on the filesystem
930 used and even the number of processors in the system. Default: true.
932 .. option:: create_fsync=bool
934 :manpage:`fsync(2)` the data file after creation. This is the default.
936 .. option:: create_on_open=bool
938 If true, don't pre-create files but allow the job's open() to create a file
939 when it's time to do I/O. Default: false -- pre-create all necessary files
942 .. option:: create_only=bool
944 If true, fio will only run the setup phase of the job. If files need to be
945 laid out or updated on disk, only that will be done -- the actual job contents
946 are not executed. Default: false.
948 .. option:: allow_file_create=bool
950 If true, fio is permitted to create files as part of its workload. If this
951 option is false, then fio will error out if
952 the files it needs to use don't already exist. Default: true.
954 .. option:: allow_mounted_write=bool
956 If this isn't set, fio will abort jobs that are destructive (e.g. that write)
957 to what appears to be a mounted device or partition. This should help catch
958 creating inadvertently destructive tests, not realizing that the test will
959 destroy data on the mounted file system. Note that some platforms don't allow
960 writing against a mounted device regardless of this option. Default: false.
962 .. option:: pre_read=bool
964 If this is given, files will be pre-read into memory before starting the
965 given I/O operation. This will also clear the :option:`invalidate` flag,
966 since it is pointless to pre-read and then drop the cache. This will only
967 work for I/O engines that are seek-able, since they allow you to read the
968 same data multiple times. Thus it will not work on non-seekable I/O engines
969 (e.g. network, splice). Default: false.
971 .. option:: unlink=bool
973 Unlink the job files when done. Not the default, as repeated runs of that
974 job would then waste time recreating the file set again and again. Default:
977 .. option:: unlink_each_loop=bool
979 Unlink job files after each iteration or loop. Default: false.
981 .. option:: zonemode=str
986 The :option:`zonerange`, :option:`zonesize`,
987 :option `zonecapacity` and option:`zoneskip`
988 parameters are ignored.
990 I/O happens in a single zone until
991 :option:`zonesize` bytes have been transferred.
992 After that number of bytes has been
993 transferred processing of the next zone
994 starts. :option `zonecapacity` is ignored.
996 Zoned block device mode. I/O happens
997 sequentially in each zone, even if random I/O
998 has been selected. Random I/O happens across
999 all zones instead of being restricted to a
1000 single zone. The :option:`zoneskip` parameter
1001 is ignored. :option:`zonerange` and
1002 :option:`zonesize` must be identical.
1003 Trim is handled using a zone reset operation.
1004 Trim only considers non-empty sequential write
1005 required and sequential write preferred zones.
1007 .. option:: zonerange=int
1009 Size of a single zone. See also :option:`zonesize` and
1012 .. option:: zonesize=int
1014 For :option:`zonemode` =strided, this is the number of bytes to
1015 transfer before skipping :option:`zoneskip` bytes. If this parameter
1016 is smaller than :option:`zonerange` then only a fraction of each zone
1017 with :option:`zonerange` bytes will be accessed. If this parameter is
1018 larger than :option:`zonerange` then each zone will be accessed
1019 multiple times before skipping to the next zone.
1021 For :option:`zonemode` =zbd, this is the size of a single zone. The
1022 :option:`zonerange` parameter is ignored in this mode.
1025 .. option:: zonecapacity=int
1027 For :option:`zonemode` =zbd, this defines the capacity of a single zone,
1028 which is the accessible area starting from the zone start address.
1029 This parameter only applies when using :option:`zonemode` =zbd in
1030 combination with regular block devices. If not specified it defaults to
1031 the zone size. If the target device is a zoned block device, the zone
1032 capacity is obtained from the device information and this option is
1035 .. option:: zoneskip=int
1037 For :option:`zonemode` =strided, the number of bytes to skip after
1038 :option:`zonesize` bytes of data have been transferred. This parameter
1039 must be zero for :option:`zonemode` =zbd.
1041 .. option:: read_beyond_wp=bool
1043 This parameter applies to :option:`zonemode` =zbd only.
1045 Zoned block devices are block devices that consist of multiple zones.
1046 Each zone has a type, e.g. conventional or sequential. A conventional
1047 zone can be written at any offset that is a multiple of the block
1048 size. Sequential zones must be written sequentially. The position at
1049 which a write must occur is called the write pointer. A zoned block
1050 device can be either drive managed, host managed or host aware. For
1051 host managed devices the host must ensure that writes happen
1052 sequentially. Fio recognizes host managed devices and serializes
1053 writes to sequential zones for these devices.
1055 If a read occurs in a sequential zone beyond the write pointer then
1056 the zoned block device will complete the read without reading any data
1057 from the storage medium. Since such reads lead to unrealistically high
1058 bandwidth and IOPS numbers fio only reads beyond the write pointer if
1059 explicitly told to do so. Default: false.
1061 .. option:: max_open_zones=int
1063 When a zone of a zoned block device is partially written (i.e. not all
1064 sectors of the zone have been written), the zone is in one of three
1065 conditions: 'implicit open', 'explicit open' or 'closed'. Zoned block
1066 devices may have a limit called 'max_open_zones' (same name as the
1067 parameter) on the total number of zones that can simultaneously be in
1068 the 'implicit open' or 'explicit open' conditions. Zoned block devices
1069 may have another limit called 'max_active_zones', on the total number of
1070 zones that can simultaneously be in the three conditions. The
1071 :option:`max_open_zones` parameter limits the number of zones to which
1072 write commands are issued by all fio jobs, that is, limits the number of
1073 zones that will be in the conditions. When the device has the
1074 max_open_zones limit and does not have the max_active_zones limit, the
1075 :option:`max_open_zones` parameter limits the number of zones in the two
1076 open conditions up to the limit. In this case, fio includes zones in the
1077 two open conditions to the write target zones at fio start. When the
1078 device has both the max_open_zones and the max_active_zones limits, the
1079 :option:`max_open_zones` parameter limits the number of zones in the
1080 three conditions up to the limit. In this case, fio includes zones in
1081 the three conditions to the write target zones at fio start.
1083 This parameter is relevant only if the :option:`zonemode` =zbd is used.
1084 The default value is always equal to the max_open_zones limit of the
1085 target zoned block device and a value higher than this limit cannot be
1086 specified by users unless the option :option:`ignore_zone_limits` is
1087 specified. When :option:`ignore_zone_limits` is specified or the target
1088 device does not have the max_open_zones limit, :option:`max_open_zones`
1089 can specify 0 to disable any limit on the number of zones that can be
1090 simultaneously written to by all jobs.
1092 .. option:: job_max_open_zones=int
1094 In the same manner as :option:`max_open_zones`, limit the number of open
1095 zones per fio job, that is, the number of zones that a single job can
1096 simultaneously write to. A value of zero indicates no limit.
1099 .. option:: ignore_zone_limits=bool
1101 If this option is used, fio will ignore the maximum number of open
1102 zones limit of the zoned block device in use, thus allowing the
1103 option :option:`max_open_zones` value to be larger than the device
1104 reported limit. Default: false.
1106 .. option:: zone_reset_threshold=float
1108 A number between zero and one that indicates the ratio of written bytes
1109 in the zones with write pointers in the IO range to the size of the IO
1110 range. When current ratio is above this ratio, zones are reset
1111 periodically as :option:`zone_reset_frequency` specifies. If there are
1112 multiple jobs when using this option, the IO range for all write jobs
1115 .. option:: zone_reset_frequency=float
1117 A number between zero and one that indicates how often a zone reset
1118 should be issued if the zone reset threshold has been exceeded. A zone
1119 reset is submitted after each (1 / zone_reset_frequency) write
1120 requests. This and the previous parameter can be used to simulate
1121 garbage collection activity.
1127 .. option:: direct=bool
1129 If value is true, use non-buffered I/O. This is usually O_DIRECT. Note that
1130 OpenBSD and ZFS on Solaris don't support direct I/O. On Windows the synchronous
1131 ioengines don't support direct I/O. Default: false.
1133 .. option:: buffered=bool
1135 If value is true, use buffered I/O. This is the opposite of the
1136 :option:`direct` option. Defaults to true.
1138 .. option:: readwrite=str, rw=str
1140 Type of I/O pattern. Accepted values are:
1147 Sequential trims (Linux block devices and SCSI
1148 character devices only).
1154 Random trims (Linux block devices and SCSI
1155 character devices only).
1157 Sequential mixed reads and writes.
1159 Random mixed reads and writes.
1161 Sequential trim+write sequences. Blocks will be trimmed first,
1162 then the same blocks will be written to. So if ``io_size=64K``
1163 is specified, Fio will trim a total of 64K bytes and also
1164 write 64K bytes on the same trimmed blocks. This behaviour
1165 will be consistent with ``number_ios`` or other Fio options
1166 limiting the total bytes or number of I/O's.
1168 Like trimwrite, but uses random offsets rather
1169 than sequential writes.
1171 Fio defaults to read if the option is not specified. For the mixed I/O
1172 types, the default is to split them 50/50. For certain types of I/O the
1173 result may still be skewed a bit, since the speed may be different.
1175 It is possible to specify the number of I/Os to do before getting a new
1176 offset by appending ``:<nr>`` to the end of the string given. For a
1177 random read, it would look like ``rw=randread:8`` for passing in an offset
1178 modifier with a value of 8. If the suffix is used with a sequential I/O
1179 pattern, then the *<nr>* value specified will be **added** to the generated
1180 offset for each I/O turning sequential I/O into sequential I/O with holes.
1181 For instance, using ``rw=write:4k`` will skip 4k for every write. Also see
1182 the :option:`rw_sequencer` option.
1184 .. option:: rw_sequencer=str
1186 If an offset modifier is given by appending a number to the ``rw=<str>``
1187 line, then this option controls how that number modifies the I/O offset
1188 being generated. Accepted values are:
1191 Generate sequential offset.
1193 Generate the same offset.
1195 ``sequential`` is only useful for random I/O, where fio would normally
1196 generate a new random offset for every I/O. If you append e.g. 8 to
1197 randread, i.e. ``rw=randread:8`` you would get a new random offset for
1198 every 8 I/Os. The result would be a sequence of 8 sequential offsets
1199 with a random starting point. However this behavior may change if a
1200 sequential I/O reaches end of the file. As sequential I/O is already
1201 sequential, setting ``sequential`` for that would not result in any
1202 difference. ``identical`` behaves in a similar fashion, except it sends
1203 the same offset 8 number of times before generating a new offset.
1208 rw_sequencer=sequential
1211 The generated sequence of offsets will look like this:
1212 4k, 8k, 12k, 16k, 20k, 24k, 28k, 32k, 92k, 96k, 100k, 104k, 108k,
1213 112k, 116k, 120k, 48k, 52k ...
1218 rw_sequencer=identical
1221 The generated sequence of offsets will look like this:
1222 4k, 4k, 4k, 4k, 4k, 4k, 4k, 4k, 92k, 92k, 92k, 92k, 92k, 92k, 92k, 92k,
1225 .. option:: unified_rw_reporting=str
1227 Fio normally reports statistics on a per data direction basis, meaning that
1228 reads, writes, and trims are accounted and reported separately. This option
1229 determines whether fio reports the results normally, summed together, or as
1231 Accepted values are:
1234 Normal statistics reporting.
1237 Statistics are summed per data direction and reported together.
1240 Statistics are reported normally, followed by the mixed statistics.
1243 Backward-compatible alias for **none**.
1246 Backward-compatible alias for **mixed**.
1251 .. option:: randrepeat=bool
1253 Seed all random number generators in a predictable way so the pattern
1254 is repeatable across runs. Default: true.
1256 .. option:: allrandrepeat=bool
1258 Alias for :option:`randrepeat`. Default: true.
1260 .. option:: randseed=int
1262 Seed the random number generators based on this seed value, to be able to
1263 control what sequence of output is being generated. If not set, the random
1264 sequence depends on the :option:`randrepeat` setting.
1266 .. option:: fallocate=str
1268 Whether pre-allocation is performed when laying down files.
1269 Accepted values are:
1272 Do not pre-allocate space.
1275 Use a platform's native pre-allocation call but fall back to
1276 **none** behavior if it fails/is not implemented.
1279 Pre-allocate via :manpage:`posix_fallocate(3)`.
1282 Pre-allocate via :manpage:`fallocate(2)` with
1283 FALLOC_FL_KEEP_SIZE set.
1286 Extend file to final size via :manpage:`ftruncate(2)`
1287 instead of allocating.
1290 Backward-compatible alias for **none**.
1293 Backward-compatible alias for **posix**.
1295 May not be available on all supported platforms. **keep** is only available
1296 on Linux. If using ZFS on Solaris this cannot be set to **posix**
1297 because ZFS doesn't support pre-allocation. Default: **native** if any
1298 pre-allocation methods except **truncate** are available, **none** if not.
1300 Note that using **truncate** on Windows will interact surprisingly
1301 with non-sequential write patterns. When writing to a file that has
1302 been extended by setting the end-of-file information, Windows will
1303 backfill the unwritten portion of the file up to that offset with
1304 zeroes before issuing the new write. This means that a single small
1305 write to the end of an extended file will stall until the entire
1306 file has been filled with zeroes.
1308 .. option:: fadvise_hint=str
1310 Use :manpage:`posix_fadvise(2)` or :manpage:`posix_fadvise(2)` to
1311 advise the kernel on what I/O patterns are likely to be issued.
1312 Accepted values are:
1315 Backwards-compatible hint for "no hint".
1318 Backwards compatible hint for "advise with fio workload type". This
1319 uses **FADV_RANDOM** for a random workload, and **FADV_SEQUENTIAL**
1320 for a sequential workload.
1323 Advise using **FADV_SEQUENTIAL**.
1326 Advise using **FADV_RANDOM**.
1329 Advise using **FADV_NOREUSE**. This may be a no-op on older Linux
1330 kernels. Since Linux 6.3, it provides a hint to the LRU algorithm.
1331 See the :manpage:`posix_fadvise(2)` man page.
1333 .. option:: write_hint=str
1335 Use :manpage:`fcntl(2)` to advise the kernel what life time to expect
1336 from a write. Only supported on Linux, as of version 4.13. Accepted
1340 No particular life time associated with this file.
1343 Data written to this file has a short life time.
1346 Data written to this file has a medium life time.
1349 Data written to this file has a long life time.
1352 Data written to this file has a very long life time.
1354 The values are all relative to each other, and no absolute meaning
1355 should be associated with them.
1357 .. option:: offset=int
1359 Start I/O at the provided offset in the file, given as either a fixed size in
1360 bytes, zones or a percentage. If a percentage is given, the generated offset will be
1361 aligned to the minimum ``blocksize`` or to the value of ``offset_align`` if
1362 provided. Data before the given offset will not be touched. This
1363 effectively caps the file size at `real_size - offset`. Can be combined with
1364 :option:`size` to constrain the start and end range of the I/O workload.
1365 A percentage can be specified by a number between 1 and 100 followed by '%',
1366 for example, ``offset=20%`` to specify 20%. In ZBD mode, value can be set as
1367 number of zones using 'z'.
1369 .. option:: offset_align=int
1371 If set to non-zero value, the byte offset generated by a percentage ``offset``
1372 is aligned upwards to this value. Defaults to 0 meaning that a percentage
1373 offset is aligned to the minimum block size.
1375 .. option:: offset_increment=int
1377 If this is provided, then the real offset becomes `offset + offset_increment
1378 * thread_number`, where the thread number is a counter that starts at 0 and
1379 is incremented for each sub-job (i.e. when :option:`numjobs` option is
1380 specified). This option is useful if there are several jobs which are
1381 intended to operate on a file in parallel disjoint segments, with even
1382 spacing between the starting points. Percentages can be used for this option.
1383 If a percentage is given, the generated offset will be aligned to the minimum
1384 ``blocksize`` or to the value of ``offset_align`` if provided. In ZBD mode, value can
1385 also be set as number of zones using 'z'.
1387 .. option:: number_ios=int
1389 Fio will normally perform I/Os until it has exhausted the size of the region
1390 set by :option:`size`, or if it exhaust the allocated time (or hits an error
1391 condition). With this setting, the range/size can be set independently of
1392 the number of I/Os to perform. When fio reaches this number, it will exit
1393 normally and report status. Note that this does not extend the amount of I/O
1394 that will be done, it will only stop fio if this condition is met before
1395 other end-of-job criteria.
1397 .. option:: fsync=int
1399 If writing to a file, issue an :manpage:`fsync(2)` (or its equivalent) of
1400 the dirty data for every number of blocks given. For example, if you give 32
1401 as a parameter, fio will sync the file after every 32 writes issued. If fio is
1402 using non-buffered I/O, we may not sync the file. The exception is the sg
1403 I/O engine, which synchronizes the disk cache anyway. Defaults to 0, which
1404 means fio does not periodically issue and wait for a sync to complete. Also
1405 see :option:`end_fsync` and :option:`fsync_on_close`.
1407 .. option:: fdatasync=int
1409 Like :option:`fsync` but uses :manpage:`fdatasync(2)` to only sync data and
1410 not metadata blocks. In Windows, DragonFlyBSD or OSX there is no
1411 :manpage:`fdatasync(2)` so this falls back to using :manpage:`fsync(2)`.
1412 Defaults to 0, which means fio does not periodically issue and wait for a
1413 data-only sync to complete.
1415 .. option:: write_barrier=int
1417 Make every `N-th` write a barrier write.
1419 .. option:: sync_file_range=str:int
1421 Use :manpage:`sync_file_range(2)` for every `int` number of write
1422 operations. Fio will track range of writes that have happened since the last
1423 :manpage:`sync_file_range(2)` call. `str` can currently be one or more of:
1426 SYNC_FILE_RANGE_WAIT_BEFORE
1428 SYNC_FILE_RANGE_WRITE
1430 SYNC_FILE_RANGE_WAIT_AFTER
1432 So if you do ``sync_file_range=wait_before,write:8``, fio would use
1433 ``SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE`` for every 8
1434 writes. Also see the :manpage:`sync_file_range(2)` man page. This option is
1437 .. option:: overwrite=bool
1439 If true, writes to a file will always overwrite existing data. If the file
1440 doesn't already exist, it will be created before the write phase begins. If
1441 the file exists and is large enough for the specified write phase, nothing
1442 will be done. Default: false.
1444 .. option:: end_fsync=bool
1446 If true, :manpage:`fsync(2)` file contents when a write stage has completed.
1449 .. option:: fsync_on_close=bool
1451 If true, fio will :manpage:`fsync(2)` a dirty file on close. This differs
1452 from :option:`end_fsync` in that it will happen on every file close, not
1453 just at the end of the job. Default: false.
1455 .. option:: rwmixread=int
1457 Percentage of a mixed workload that should be reads. Default: 50.
1459 .. option:: rwmixwrite=int
1461 Percentage of a mixed workload that should be writes. If both
1462 :option:`rwmixread` and :option:`rwmixwrite` is given and the values do not
1463 add up to 100%, the latter of the two will be used to override the
1464 first. This may interfere with a given rate setting, if fio is asked to
1465 limit reads or writes to a certain rate. If that is the case, then the
1466 distribution may be skewed. Default: 50.
1468 .. option:: random_distribution=str:float[:float][,str:float][,str:float]
1470 By default, fio will use a completely uniform random distribution when asked
1471 to perform random I/O. Sometimes it is useful to skew the distribution in
1472 specific ways, ensuring that some parts of the data is more hot than others.
1473 fio includes the following distribution models:
1476 Uniform random distribution
1485 Normal (Gaussian) distribution
1488 Zoned random distribution
1491 Zone absolute random distribution
1493 When using a **zipf** or **pareto** distribution, an input value is also
1494 needed to define the access pattern. For **zipf**, this is the `Zipf
1495 theta`. For **pareto**, it's the `Pareto power`. Fio includes a test
1496 program, :command:`fio-genzipf`, that can be used visualize what the given input
1497 values will yield in terms of hit rates. If you wanted to use **zipf** with
1498 a `theta` of 1.2, you would use ``random_distribution=zipf:1.2`` as the
1499 option. If a non-uniform model is used, fio will disable use of the random
1500 map. For the **normal** distribution, a normal (Gaussian) deviation is
1501 supplied as a value between 0 and 100.
1503 The second, optional float is allowed for **pareto**, **zipf** and **normal** distributions.
1504 It allows one to set base of distribution in non-default place, giving more control
1505 over most probable outcome. This value is in range [0-1] which maps linearly to
1506 range of possible random values.
1507 Defaults are: random for **pareto** and **zipf**, and 0.5 for **normal**.
1508 If you wanted to use **zipf** with a `theta` of 1.2 centered on 1/4 of allowed value range,
1509 you would use ``random_distribution=zipf:1.2:0.25``.
1511 For a **zoned** distribution, fio supports specifying percentages of I/O
1512 access that should fall within what range of the file or device. For
1513 example, given a criteria of:
1515 * 60% of accesses should be to the first 10%
1516 * 30% of accesses should be to the next 20%
1517 * 8% of accesses should be to the next 30%
1518 * 2% of accesses should be to the next 40%
1520 we can define that through zoning of the random accesses. For the above
1521 example, the user would do::
1523 random_distribution=zoned:60/10:30/20:8/30:2/40
1525 A **zoned_abs** distribution works exactly like the **zoned**, except
1526 that it takes absolute sizes. For example, let's say you wanted to
1527 define access according to the following criteria:
1529 * 60% of accesses should be to the first 20G
1530 * 30% of accesses should be to the next 100G
1531 * 10% of accesses should be to the next 500G
1533 we can define an absolute zoning distribution with:
1535 random_distribution=zoned_abs=60/20G:30/100G:10/500g
1537 For both **zoned** and **zoned_abs**, fio supports defining up to
1540 Similarly to how :option:`bssplit` works for setting ranges and
1541 percentages of block sizes. Like :option:`bssplit`, it's possible to
1542 specify separate zones for reads, writes, and trims. If just one set
1543 is given, it'll apply to all of them. This goes for both **zoned**
1544 **zoned_abs** distributions.
1546 .. option:: percentage_random=int[,int][,int]
1548 For a random workload, set how big a percentage should be random. This
1549 defaults to 100%, in which case the workload is fully random. It can be set
1550 from anywhere from 0 to 100. Setting it to 0 would make the workload fully
1551 sequential. Any setting in between will result in a random mix of sequential
1552 and random I/O, at the given percentages. Comma-separated values may be
1553 specified for reads, writes, and trims as described in :option:`blocksize`.
1555 .. option:: norandommap
1557 Normally fio will cover every block of the file when doing random I/O. If
1558 this option is given, fio will just get a new random offset without looking
1559 at past I/O history. This means that some blocks may not be read or written,
1560 and that some blocks may be read/written more than once. If this option is
1561 used with :option:`verify` and multiple blocksizes (via :option:`bsrange`),
1562 only intact blocks are verified, i.e., partially-overwritten blocks are
1563 ignored. With an async I/O engine and an I/O depth > 1, it is possible for
1564 the same block to be overwritten, which can cause verification errors. Either
1565 do not use norandommap in this case, or also use the lfsr random generator.
1567 .. option:: softrandommap=bool
1569 See :option:`norandommap`. If fio runs with the random block map enabled and
1570 it fails to allocate the map, if this option is set it will continue without
1571 a random block map. As coverage will not be as complete as with random maps,
1572 this option is disabled by default.
1574 .. option:: random_generator=str
1576 Fio supports the following engines for generating I/O offsets for random I/O:
1579 Strong 2^88 cycle random number generator.
1581 Linear feedback shift register generator.
1583 Strong 64-bit 2^258 cycle random number generator.
1585 **tausworthe** is a strong random number generator, but it requires tracking
1586 on the side if we want to ensure that blocks are only read or written
1587 once. **lfsr** guarantees that we never generate the same offset twice, and
1588 it's also less computationally expensive. It's not a true random generator,
1589 however, though for I/O purposes it's typically good enough. **lfsr** only
1590 works with single block sizes, not with workloads that use multiple block
1591 sizes. If used with such a workload, fio may read or write some blocks
1592 multiple times. The default value is **tausworthe**, unless the required
1593 space exceeds 2^32 blocks. If it does, then **tausworthe64** is
1594 selected automatically.
1600 .. option:: blocksize=int[,int][,int], bs=int[,int][,int]
1602 The block size in bytes used for I/O units. Default: 4096. A single value
1603 applies to reads, writes, and trims. Comma-separated values may be
1604 specified for reads, writes, and trims. A value not terminated in a comma
1605 applies to subsequent types.
1610 means 256k for reads, writes and trims.
1613 means 8k for reads, 32k for writes and trims.
1616 means 8k for reads, 32k for writes, and default for trims.
1619 means default for reads, 8k for writes and trims.
1622 means default for reads, 8k for writes, and default for trims.
1624 .. option:: blocksize_range=irange[,irange][,irange], bsrange=irange[,irange][,irange]
1626 A range of block sizes in bytes for I/O units. The issued I/O unit will
1627 always be a multiple of the minimum size, unless
1628 :option:`blocksize_unaligned` is set.
1630 Comma-separated ranges may be specified for reads, writes, and trims as
1631 described in :option:`blocksize`.
1633 Example: ``bsrange=1k-4k,2k-8k``.
1635 .. option:: bssplit=str[,str][,str]
1637 Sometimes you want even finer grained control of the block sizes
1638 issued, not just an even split between them. This option allows you to
1639 weight various block sizes, so that you are able to define a specific
1640 amount of block sizes issued. The format for this option is::
1642 bssplit=blocksize/percentage:blocksize/percentage
1644 for as many block sizes as needed. So if you want to define a workload
1645 that has 50% 64k blocks, 10% 4k blocks, and 40% 32k blocks, you would
1648 bssplit=4k/10:64k/50:32k/40
1650 Ordering does not matter. If the percentage is left blank, fio will
1651 fill in the remaining values evenly. So a bssplit option like this one::
1653 bssplit=4k/50:1k/:32k/
1655 would have 50% 4k ios, and 25% 1k and 32k ios. The percentages always
1656 add up to 100, if bssplit is given a range that adds up to more, it
1659 Comma-separated values may be specified for reads, writes, and trims as
1660 described in :option:`blocksize`.
1662 If you want a workload that has 50% 2k reads and 50% 4k reads, while
1663 having 90% 4k writes and 10% 8k writes, you would specify::
1665 bssplit=2k/50:4k/50,4k/90:8k/10
1667 Fio supports defining up to 64 different weights for each data
1670 .. option:: blocksize_unaligned, bs_unaligned
1672 If set, fio will issue I/O units with any size within
1673 :option:`blocksize_range`, not just multiples of the minimum size. This
1674 typically won't work with direct I/O, as that normally requires sector
1677 .. option:: bs_is_seq_rand=bool
1679 If this option is set, fio will use the normal read,write blocksize settings
1680 as sequential,random blocksize settings instead. Any random read or write
1681 will use the WRITE blocksize settings, and any sequential read or write will
1682 use the READ blocksize settings.
1684 .. option:: blockalign=int[,int][,int], ba=int[,int][,int]
1686 Boundary to which fio will align random I/O units. Default:
1687 :option:`blocksize`. Minimum alignment is typically 512b for using direct
1688 I/O, though it usually depends on the hardware block size. This option is
1689 mutually exclusive with using a random map for files, so it will turn off
1690 that option. Comma-separated values may be specified for reads, writes, and
1691 trims as described in :option:`blocksize`.
1697 .. option:: zero_buffers
1699 Initialize buffers with all zeros. Default: fill buffers with random data.
1701 .. option:: refill_buffers
1703 If this option is given, fio will refill the I/O buffers on every
1704 submit. Only makes sense if :option:`zero_buffers` isn't specified,
1705 naturally. Defaults to being unset i.e., the buffer is only filled at
1706 init time and the data in it is reused when possible but if any of
1707 :option:`verify`, :option:`buffer_compress_percentage` or
1708 :option:`dedupe_percentage` are enabled then `refill_buffers` is also
1709 automatically enabled.
1711 .. option:: scramble_buffers=bool
1713 If :option:`refill_buffers` is too costly and the target is using data
1714 deduplication, then setting this option will slightly modify the I/O buffer
1715 contents to defeat normal de-dupe attempts. This is not enough to defeat
1716 more clever block compression attempts, but it will stop naive dedupe of
1717 blocks. Default: true.
1719 .. option:: buffer_compress_percentage=int
1721 If this is set, then fio will attempt to provide I/O buffer content
1722 (on WRITEs) that compresses to the specified level. Fio does this by
1723 providing a mix of random data followed by fixed pattern data. The
1724 fixed pattern is either zeros, or the pattern specified by
1725 :option:`buffer_pattern`. If the `buffer_pattern` option is used, it
1726 might skew the compression ratio slightly. Setting
1727 `buffer_compress_percentage` to a value other than 100 will also
1728 enable :option:`refill_buffers` in order to reduce the likelihood that
1729 adjacent blocks are so similar that they over compress when seen
1730 together. See :option:`buffer_compress_chunk` for how to set a finer or
1731 coarser granularity for the random/fixed data region. Defaults to unset
1732 i.e., buffer data will not adhere to any compression level.
1734 .. option:: buffer_compress_chunk=int
1736 This setting allows fio to manage how big the random/fixed data region
1737 is when using :option:`buffer_compress_percentage`. When
1738 `buffer_compress_chunk` is set to some non-zero value smaller than the
1739 block size, fio can repeat the random/fixed region throughout the I/O
1740 buffer at the specified interval (which particularly useful when
1741 bigger block sizes are used for a job). When set to 0, fio will use a
1742 chunk size that matches the block size resulting in a single
1743 random/fixed region within the I/O buffer. Defaults to 512. When the
1744 unit is omitted, the value is interpreted in bytes.
1746 .. option:: buffer_pattern=str
1748 If set, fio will fill the I/O buffers with this pattern or with the contents
1749 of a file. If not set, the contents of I/O buffers are defined by the other
1750 options related to buffer contents. The setting can be any pattern of bytes,
1751 and can be prefixed with 0x for hex values. It may also be a string, where
1752 the string must then be wrapped with ``""``. Or it may also be a filename,
1753 where the filename must be wrapped with ``''`` in which case the file is
1754 opened and read. Note that not all the file contents will be read if that
1755 would cause the buffers to overflow. So, for example::
1757 buffer_pattern='filename'
1761 buffer_pattern="abcd"
1769 buffer_pattern=0xdeadface
1771 Also you can combine everything together in any order::
1773 buffer_pattern=0xdeadface"abcd"-12'filename'
1775 .. option:: dedupe_percentage=int
1777 If set, fio will generate this percentage of identical buffers when
1778 writing. These buffers will be naturally dedupable. The contents of the
1779 buffers depend on what other buffer compression settings have been set. It's
1780 possible to have the individual buffers either fully compressible, or not at
1781 all -- this option only controls the distribution of unique buffers. Setting
1782 this option will also enable :option:`refill_buffers` to prevent every buffer
1785 .. option:: dedupe_mode=str
1787 If ``dedupe_percentage=<int>`` is given, then this option controls how fio
1788 generates the dedupe buffers.
1791 Generate dedupe buffers by repeating previous writes
1793 Generate dedupe buffers from working set
1795 ``repeat`` is the default option for fio. Dedupe buffers are generated
1796 by repeating previous unique write.
1798 ``working_set`` is a more realistic workload.
1799 With ``working_set``, ``dedupe_working_set_percentage=<int>`` should be provided.
1800 Given that, fio will use the initial unique write buffers as its working set.
1801 Upon deciding to dedupe, fio will randomly choose a buffer from the working set.
1802 Note that by using ``working_set`` the dedupe percentage will converge
1803 to the desired over time while ``repeat`` maintains the desired percentage
1806 .. option:: dedupe_working_set_percentage=int
1808 If ``dedupe_mode=<str>`` is set to ``working_set``, then this controls
1809 the percentage of size of the file or device used as the buffers
1810 fio will choose to generate the dedupe buffers from
1812 Note that size needs to be explicitly provided and only 1 file per
1815 .. option:: dedupe_global=bool
1817 This controls whether the deduplication buffers will be shared amongst
1818 all jobs that have this option set. The buffers are spread evenly between
1821 .. option:: invalidate=bool
1823 Invalidate the buffer/page cache parts of the files to be used prior to
1824 starting I/O if the platform and file type support it. Defaults to true.
1825 This will be ignored if :option:`pre_read` is also specified for the
1828 .. option:: sync=str
1830 Whether, and what type, of synchronous I/O to use for writes. The allowed
1834 Do not use synchronous IO, the default.
1840 Use synchronous file IO. For the majority of I/O engines,
1841 this means using O_SYNC.
1847 Use synchronous data IO. For the majority of I/O engines,
1848 this means using O_DSYNC.
1851 .. option:: iomem=str, mem=str
1853 Fio can use various types of memory as the I/O unit buffer. The allowed
1857 Use memory from :manpage:`malloc(3)` as the buffers. Default memory
1861 Use shared memory as the buffers. Allocated through
1862 :manpage:`shmget(2)`.
1865 Same as shm, but use huge pages as backing.
1868 Use :manpage:`mmap(2)` to allocate buffers. May either be anonymous memory, or can
1869 be file backed if a filename is given after the option. The format
1870 is `mem=mmap:/path/to/file`.
1873 Use a memory mapped huge file as the buffer backing. Append filename
1874 after mmaphuge, ala `mem=mmaphuge:/hugetlbfs/file`.
1877 Same as mmap, but use a MMAP_SHARED mapping.
1880 Use GPU memory as the buffers for GPUDirect RDMA benchmark.
1881 The :option:`ioengine` must be `rdma`.
1883 The area allocated is a function of the maximum allowed bs size for the job,
1884 multiplied by the I/O depth given. Note that for **shmhuge** and
1885 **mmaphuge** to work, the system must have free huge pages allocated. This
1886 can normally be checked and set by reading/writing
1887 :file:`/proc/sys/vm/nr_hugepages` on a Linux system. Fio assumes a huge page
1888 is 2 or 4MiB in size depending on the platform. So to calculate the
1889 number of huge pages you need for a given job file, add up the I/O
1890 depth of all jobs (normally one unless :option:`iodepth` is used) and
1891 multiply by the maximum bs set. Then divide that number by the huge
1892 page size. You can see the size of the huge pages in
1893 :file:`/proc/meminfo`. If no huge pages are allocated by having a
1894 non-zero number in `nr_hugepages`, using **mmaphuge** or **shmhuge**
1895 will fail. Also see :option:`hugepage-size`.
1897 **mmaphuge** also needs to have hugetlbfs mounted and the file location
1898 should point there. So if it's mounted in :file:`/huge`, you would use
1899 `mem=mmaphuge:/huge/somefile`.
1901 .. option:: iomem_align=int, mem_align=int
1903 This indicates the memory alignment of the I/O memory buffers. Note that
1904 the given alignment is applied to the first I/O unit buffer, if using
1905 :option:`iodepth` the alignment of the following buffers are given by the
1906 :option:`bs` used. In other words, if using a :option:`bs` that is a
1907 multiple of the page sized in the system, all buffers will be aligned to
1908 this value. If using a :option:`bs` that is not page aligned, the alignment
1909 of subsequent I/O memory buffers is the sum of the :option:`iomem_align` and
1912 .. option:: hugepage-size=int
1914 Defines the size of a huge page. Must at least be equal to the system
1915 setting, see :file:`/proc/meminfo` and
1916 :file:`/sys/kernel/mm/hugepages/`. Defaults to 2 or 4MiB depending on
1917 the platform. Should probably always be a multiple of megabytes, so
1918 using ``hugepage-size=Xm`` is the preferred way to set this to avoid
1919 setting a non-pow-2 bad value.
1921 .. option:: lockmem=int
1923 Pin the specified amount of memory with :manpage:`mlock(2)`. Can be used to
1924 simulate a smaller amount of memory. The amount specified is per worker.
1930 .. option:: size=int
1932 The total size of file I/O for each thread of this job. Fio will run until
1933 this many bytes has been transferred, unless runtime is altered by other means
1934 such as (1) :option:`runtime`, (2) :option:`io_size` (3) :option:`number_ios`,
1935 (4) gaps/holes while doing I/O's such as ``rw=read:16K``, or (5) sequential
1936 I/O reaching end of the file which is possible when :option:`percentage_random`
1938 Fio will divide this size between the available files determined by options
1939 such as :option:`nrfiles`, :option:`filename`, unless :option:`filesize` is
1940 specified by the job. If the result of division happens to be 0, the size is
1941 set to the physical size of the given files or devices if they exist.
1942 If this option is not specified, fio will use the full size of the given
1943 files or devices. If the files do not exist, size must be given. It is also
1944 possible to give size as a percentage between 1 and 100. If ``size=20%`` is
1945 given, fio will use 20% of the full size of the given files or devices.
1946 In ZBD mode, value can also be set as number of zones using 'z'.
1947 Can be combined with :option:`offset` to constrain the start and end range
1948 that I/O will be done within.
1950 .. option:: io_size=int, io_limit=int
1952 Normally fio operates within the region set by :option:`size`, which means
1953 that the :option:`size` option sets both the region and size of I/O to be
1954 performed. Sometimes that is not what you want. With this option, it is
1955 possible to define just the amount of I/O that fio should do. For instance,
1956 if :option:`size` is set to 20GiB and :option:`io_size` is set to 5GiB, fio
1957 will perform I/O within the first 20GiB but exit when 5GiB have been
1958 done. The opposite is also possible -- if :option:`size` is set to 20GiB,
1959 and :option:`io_size` is set to 40GiB, then fio will do 40GiB of I/O within
1960 the 0..20GiB region.
1962 .. option:: filesize=irange(int)
1964 Individual file sizes. May be a range, in which case fio will select sizes for
1965 files at random within the given range. If not given, each created file is the
1966 same size. This option overrides :option:`size` in terms of file size, i.e. if
1967 :option:`filesize` is specified then :option:`size` becomes merely the default
1968 for :option:`io_size` and has no effect at all if :option:`io_size` is set
1971 .. option:: file_append=bool
1973 Perform I/O after the end of the file. Normally fio will operate within the
1974 size of a file. If this option is set, then fio will append to the file
1975 instead. This has identical behavior to setting :option:`offset` to the size
1976 of a file. This option is ignored on non-regular files.
1978 .. option:: fill_device=bool, fill_fs=bool
1980 Sets size to something really large and waits for ENOSPC (no space left on
1981 device) or EDQUOT (disk quota exceeded)
1982 as the terminating condition. Only makes sense with sequential
1983 write. For a read workload, the mount point will be filled first then I/O
1984 started on the result. This option doesn't make sense if operating on a raw
1985 device node, since the size of that is already known by the file system.
1986 Additionally, writing beyond end-of-device will not return ENOSPC there.
1992 .. option:: ioengine=str
1994 Defines how the job issues I/O to the file. The following types are defined:
1997 Basic :manpage:`read(2)` or :manpage:`write(2)`
1998 I/O. :manpage:`lseek(2)` is used to position the I/O location.
1999 See :option:`fsync` and :option:`fdatasync` for syncing write I/Os.
2002 Basic :manpage:`pread(2)` or :manpage:`pwrite(2)` I/O. Default on
2003 all supported operating systems except for Windows.
2006 Basic :manpage:`readv(2)` or :manpage:`writev(2)` I/O. Will emulate
2007 queuing by coalescing adjacent I/Os into a single submission.
2010 Basic :manpage:`preadv(2)` or :manpage:`pwritev(2)` I/O.
2013 Basic :manpage:`preadv2(2)` or :manpage:`pwritev2(2)` I/O.
2016 Fast Linux native asynchronous I/O. Supports async IO
2017 for both direct and buffered IO.
2018 This engine defines engine specific options.
2021 Fast Linux native asynchronous I/O for pass through commands.
2022 This engine defines engine specific options.
2025 Linux native asynchronous I/O. Note that Linux may only support
2026 queued behavior with non-buffered I/O (set ``direct=1`` or
2028 This engine defines engine specific options.
2031 POSIX asynchronous I/O using :manpage:`aio_read(3)` and
2032 :manpage:`aio_write(3)`.
2035 Solaris native asynchronous I/O.
2038 Windows native asynchronous I/O. Default on Windows.
2041 File is memory mapped with :manpage:`mmap(2)` and data copied
2042 to/from using :manpage:`memcpy(3)`.
2045 :manpage:`splice(2)` is used to transfer the data and
2046 :manpage:`vmsplice(2)` to transfer data from user space to the
2050 SCSI generic sg v3 I/O. May either be synchronous using the SG_IO
2051 ioctl, or if the target is an sg character device we use
2052 :manpage:`read(2)` and :manpage:`write(2)` for asynchronous
2053 I/O. Requires :option:`filename` option to specify either block or
2054 character devices. This engine supports trim operations.
2055 The sg engine includes engine specific options.
2058 Read, write, trim and ZBC/ZAC operations to a zoned
2059 block device using libzbc library. The target can be
2060 either an SG character device or a block device file.
2063 Doesn't transfer any data, just pretends to. This is mainly used to
2064 exercise fio itself and for debugging/testing purposes.
2067 Transfer over the network to given ``host:port``. Depending on the
2068 :option:`protocol` used, the :option:`hostname`, :option:`port`,
2069 :option:`listen` and :option:`filename` options are used to specify
2070 what sort of connection to make, while the :option:`protocol` option
2071 determines which protocol will be used. This engine defines engine
2075 Like **net**, but uses :manpage:`splice(2)` and
2076 :manpage:`vmsplice(2)` to map data and send/receive.
2077 This engine defines engine specific options.
2080 Doesn't transfer any data, but burns CPU cycles according to the
2081 :option:`cpuload`, :option:`cpuchunks` and :option:`cpumode` options.
2082 Setting :option:`cpuload`\=85 will cause that job to do nothing but burn 85%
2083 of the CPU. In case of SMP machines, use :option:`numjobs`\=<nr_of_cpu>
2084 to get desired CPU usage, as the cpuload only loads a
2085 single CPU at the desired rate. A job never finishes unless there is
2086 at least one non-cpuio job.
2087 Setting :option:`cpumode`\=qsort replace the default noop instructions loop
2088 by a qsort algorithm to consume more energy.
2091 The RDMA I/O engine supports both RDMA memory semantics
2092 (RDMA_WRITE/RDMA_READ) and channel semantics (Send/Recv) for the
2093 InfiniBand, RoCE and iWARP protocols. This engine defines engine
2097 I/O engine that does regular fallocate to simulate data transfer as
2101 does fallocate(,mode = FALLOC_FL_KEEP_SIZE,).
2104 does fallocate(,mode = 0).
2107 does fallocate(,mode = FALLOC_FL_KEEP_SIZE|FALLOC_FL_PUNCH_HOLE).
2110 I/O engine that sends :manpage:`ftruncate(2)` operations in response
2111 to write (DDIR_WRITE) events. Each ftruncate issued sets the file's
2112 size to the current block offset. :option:`blocksize` is ignored.
2115 I/O engine that does regular EXT4_IOC_MOVE_EXT ioctls to simulate
2116 defragment activity in request to DDIR_WRITE event.
2119 I/O engine supporting direct access to Ceph Reliable Autonomic
2120 Distributed Object Store (RADOS) via librados. This ioengine
2121 defines engine specific options.
2124 I/O engine supporting direct access to Ceph Rados Block Devices
2125 (RBD) via librbd without the need to use the kernel rbd driver. This
2126 ioengine defines engine specific options.
2129 I/O engine supporting GET/PUT requests over HTTP(S) with libcurl to
2130 a WebDAV or S3 endpoint. This ioengine defines engine specific options.
2132 This engine only supports direct IO of iodepth=1; you need to scale this
2133 via numjobs. blocksize defines the size of the objects to be created.
2135 TRIM is translated to object deletion.
2138 Using GlusterFS libgfapi sync interface to direct access to
2139 GlusterFS volumes without having to go through FUSE. This ioengine
2140 defines engine specific options.
2143 Using GlusterFS libgfapi async interface to direct access to
2144 GlusterFS volumes without having to go through FUSE. This ioengine
2145 defines engine specific options.
2148 Read and write through Hadoop (HDFS). The :option:`filename` option
2149 is used to specify host,port of the hdfs name-node to connect. This
2150 engine interprets offsets a little differently. In HDFS, files once
2151 created cannot be modified so random writes are not possible. To
2152 imitate this the libhdfs engine expects a bunch of small files to be
2153 created over HDFS and will randomly pick a file from them
2154 based on the offset generated by fio backend (see the example
2155 job file to create such files, use ``rw=write`` option). Please
2156 note, it may be necessary to set environment variables to work
2157 with HDFS/libhdfs properly. Each job uses its own connection to
2161 Read, write and erase an MTD character device (e.g.,
2162 :file:`/dev/mtd0`). Discards are treated as erases. Depending on the
2163 underlying device type, the I/O may have to go in a certain pattern,
2164 e.g., on NAND, writing sequentially to erase blocks and discarding
2165 before overwriting. The `trimwrite` mode works well for this
2169 Read and write using device DAX to a persistent memory device (e.g.,
2170 /dev/dax0.0) through the PMDK libpmem library.
2173 Prefix to specify loading an external I/O engine object file. Append
2174 the engine filename, e.g. ``ioengine=external:/tmp/foo.o`` to load
2175 ioengine :file:`foo.o` in :file:`/tmp`. The path can be either
2176 absolute or relative. See :file:`engines/skeleton_external.c` for
2177 details of writing an external I/O engine.
2180 Simply create the files and do no I/O to them. You still need to
2181 set `filesize` so that all the accounting still occurs, but no
2182 actual I/O will be done other than creating the file.
2185 Simply do stat() and do no I/O to the file. You need to set 'filesize'
2186 and 'nrfiles', so that files will be created.
2187 This engine is to measure file lookup and meta data access.
2190 Simply delete the files by unlink() and do no I/O to them. You need to set 'filesize'
2191 and 'nrfiles', so that the files will be created.
2192 This engine is to measure file delete.
2195 Read and write using mmap I/O to a file on a filesystem
2196 mounted with DAX on a persistent memory device through the PMDK
2200 Synchronous read and write using DDN's Infinite Memory Engine (IME).
2201 This engine is very basic and issues calls to IME whenever an IO is
2205 Synchronous read and write using DDN's Infinite Memory Engine (IME).
2206 This engine uses iovecs and will try to stack as much IOs as possible
2207 (if the IOs are "contiguous" and the IO depth is not exceeded)
2208 before issuing a call to IME.
2211 Asynchronous read and write using DDN's Infinite Memory Engine (IME).
2212 This engine will try to stack as much IOs as possible by creating
2213 requests for IME. FIO will then decide when to commit these requests.
2216 Read and write iscsi lun with libiscsi.
2219 Read and write a Network Block Device (NBD).
2222 I/O engine supporting libcufile synchronous access to nvidia-fs and a
2223 GPUDirect Storage-supported filesystem. This engine performs
2224 I/O without transferring buffers between user-space and the kernel,
2225 unless :option:`verify` is set or :option:`cuda_io` is `posix`.
2226 :option:`iomem` must not be `cudamalloc`. This ioengine defines
2227 engine specific options.
2230 I/O engine supporting asynchronous read and write operations to the
2231 DAOS File System (DFS) via libdfs.
2234 I/O engine supporting asynchronous read and write operations to
2235 NFS filesystems from userspace via libnfs. This is useful for
2236 achieving higher concurrency and thus throughput than is possible
2240 Execute 3rd party tools. Could be used to perform monitoring during jobs runtime.
2243 I/O engine using the xNVMe C API, for NVMe devices. The xnvme engine provides
2244 flexibility to access GNU/Linux Kernel NVMe driver via libaio, IOCTLs, io_uring,
2245 the SPDK NVMe driver, or your own custom NVMe driver. The xnvme engine includes
2246 engine specific options. (See https://xnvme.io).
2249 Use the libblkio library
2250 (https://gitlab.com/libblkio/libblkio). The specific
2251 *driver* to use must be set using
2252 :option:`libblkio_driver`. If
2253 :option:`mem`/:option:`iomem` is not specified, memory
2254 allocation is delegated to libblkio (and so is
2255 guaranteed to work with the selected *driver*). One
2256 libblkio instance is used per process, so all jobs
2257 setting option :option:`thread` will share a single
2258 instance (with one queue per thread) and must specify
2259 compatible options. Note that some drivers don't allow
2260 several instances to access the same device or file
2261 simultaneously, but allow it for threads.
2263 I/O engine specific parameters
2264 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2266 In addition, there are some parameters which are only valid when a specific
2267 :option:`ioengine` is in use. These are used identically to normal parameters,
2268 with the caveat that when used on the command line, they must come after the
2269 :option:`ioengine` that defines them is selected.
2271 .. option:: cmdprio_percentage=int[,int] : [io_uring] [libaio]
2273 Set the percentage of I/O that will be issued with the highest priority.
2274 Default: 0. A single value applies to reads and writes. Comma-separated
2275 values may be specified for reads and writes. For this option to be
2276 effective, NCQ priority must be supported and enabled, and the :option:`direct`
2277 option must be set. fio must also be run as the root user. Unlike
2278 slat/clat/lat stats, which can be tracked and reported independently, per
2279 priority stats only track and report a single type of latency. By default,
2280 completion latency (clat) will be reported, if :option:`lat_percentiles` is
2281 set, total latency (lat) will be reported.
2283 .. option:: cmdprio_class=int[,int] : [io_uring] [libaio]
2285 Set the I/O priority class to use for I/Os that must be issued with
2286 a priority when :option:`cmdprio_percentage` or
2287 :option:`cmdprio_bssplit` is set. If not specified when
2288 :option:`cmdprio_percentage` or :option:`cmdprio_bssplit` is set,
2289 this defaults to the highest priority class. A single value applies
2290 to reads and writes. Comma-separated values may be specified for
2291 reads and writes. See :manpage:`ionice(1)`. See also the
2292 :option:`prioclass` option.
2294 .. option:: cmdprio_hint=int[,int] : [io_uring] [libaio]
2296 Set the I/O priority hint to use for I/Os that must be issued with
2297 a priority when :option:`cmdprio_percentage` or
2298 :option:`cmdprio_bssplit` is set. If not specified when
2299 :option:`cmdprio_percentage` or :option:`cmdprio_bssplit` is set,
2300 this defaults to 0 (no hint). A single value applies to reads and
2301 writes. Comma-separated values may be specified for reads and writes.
2302 See also the :option:`priohint` option.
2304 .. option:: cmdprio=int[,int] : [io_uring] [libaio]
2306 Set the I/O priority value to use for I/Os that must be issued with
2307 a priority when :option:`cmdprio_percentage` or
2308 :option:`cmdprio_bssplit` is set. If not specified when
2309 :option:`cmdprio_percentage` or :option:`cmdprio_bssplit` is set,
2311 Linux limits us to a positive value between 0 and 7, with 0 being the
2312 highest. A single value applies to reads and writes. Comma-separated
2313 values may be specified for reads and writes. See :manpage:`ionice(1)`.
2314 Refer to an appropriate manpage for other operating systems since
2315 meaning of priority may differ. See also the :option:`prio` option.
2317 .. option:: cmdprio_bssplit=str[,str] : [io_uring] [libaio]
2319 To get a finer control over I/O priority, this option allows
2320 specifying the percentage of IOs that must have a priority set
2321 depending on the block size of the IO. This option is useful only
2322 when used together with the :option:`bssplit` option, that is,
2323 multiple different block sizes are used for reads and writes.
2325 The first accepted format for this option is the same as the format of
2326 the :option:`bssplit` option:
2328 cmdprio_bssplit=blocksize/percentage:blocksize/percentage
2330 In this case, each entry will use the priority class, priority hint
2331 and priority level defined by the options :option:`cmdprio_class`,
2332 :option:`cmdprio` and :option:`cmdprio_hint` respectively.
2334 The second accepted format for this option is:
2336 cmdprio_bssplit=blocksize/percentage/class/level:blocksize/percentage/class/level
2338 In this case, the priority class and priority level is defined inside
2339 each entry. In comparison with the first accepted format, the second
2340 accepted format does not restrict all entries to have the same priority
2341 class and priority level.
2343 The third accepted format for this option is:
2345 cmdprio_bssplit=blocksize/percentage/class/level/hint:...
2347 This is an extension of the second accepted format that allows to also
2348 specify a priority hint.
2350 For all formats, only the read and write data directions are supported,
2351 values for trim IOs are ignored. This option is mutually exclusive with
2352 the :option:`cmdprio_percentage` option.
2354 .. option:: fixedbufs : [io_uring] [io_uring_cmd]
2356 If fio is asked to do direct IO, then Linux will map pages for each
2357 IO call, and release them when IO is done. If this option is set, the
2358 pages are pre-mapped before IO is started. This eliminates the need to
2359 map and release for each IO. This is more efficient, and reduces the
2362 .. option:: nonvectored=int : [io_uring] [io_uring_cmd]
2364 With this option, fio will use non-vectored read/write commands, where
2365 address must contain the address directly. Default is -1.
2367 .. option:: force_async=int : [io_uring] [io_uring_cmd]
2369 Normal operation for io_uring is to try and issue an sqe as
2370 non-blocking first, and if that fails, execute it in an async manner.
2371 With this option set to N, then every N request fio will ask sqe to
2372 be issued in an async manner. Default is 0.
2374 .. option:: registerfiles : [io_uring] [io_uring_cmd]
2376 With this option, fio registers the set of files being used with the
2377 kernel. This avoids the overhead of managing file counts in the kernel,
2378 making the submission and completion part more lightweight. Required
2379 for the below :option:`sqthread_poll` option.
2381 .. option:: sqthread_poll : [io_uring] [io_uring_cmd] [xnvme]
2383 Normally fio will submit IO by issuing a system call to notify the
2384 kernel of available items in the SQ ring. If this option is set, the
2385 act of submitting IO will be done by a polling thread in the kernel.
2386 This frees up cycles for fio, at the cost of using more CPU in the
2387 system. As submission is just the time it takes to fill in the sqe
2388 entries and any syscall required to wake up the idle kernel thread,
2389 fio will not report submission latencies.
2391 .. option:: sqthread_poll_cpu=int : [io_uring] [io_uring_cmd]
2393 When :option:`sqthread_poll` is set, this option provides a way to
2394 define which CPU should be used for the polling thread.
2396 .. option:: cmd_type=str : [io_uring_cmd]
2398 Specifies the type of uring passthrough command to be used. Supported
2399 value is nvme. Default is nvme.
2403 [io_uring] [io_uring_cmd] [xnvme]
2405 If this option is set, fio will attempt to use polled IO completions.
2406 Normal IO completions generate interrupts to signal the completion of
2407 IO, polled completions do not. Hence they are require active reaping
2408 by the application. The benefits are more efficient IO for high IOPS
2409 scenarios, and lower latencies for low queue depth IO.
2413 Use poll queues. This is incompatible with
2414 :option:`libblkio_wait_mode=eventfd <libblkio_wait_mode>` and
2415 :option:`libblkio_force_enable_completion_eventfd`.
2419 Set RWF_HIPRI on I/O, indicating to the kernel that it's of higher priority
2424 If this option is set, fio will attempt to use polled IO completions.
2425 This will have a similar effect as (io_uring)hipri. Only SCSI READ and
2426 WRITE commands will have the SGV4_FLAG_HIPRI set (not UNMAP (trim) nor
2427 VERIFY). Older versions of the Linux sg driver that do not support
2428 hipri will simply ignore this flag and do normal IO. The Linux SCSI
2429 Low Level Driver (LLD) that "owns" the device also needs to support
2430 hipri (also known as iopoll and mq_poll). The MegaRAID driver is an
2431 example of a SCSI LLD. Default: clear (0) which does normal
2432 (interrupted based) IO.
2434 .. option:: userspace_reap : [libaio]
2436 Normally, with the libaio engine in use, fio will use the
2437 :manpage:`io_getevents(2)` system call to reap newly returned events. With
2438 this flag turned on, the AIO ring will be read directly from user-space to
2439 reap events. The reaping mode is only enabled when polling for a minimum of
2440 0 events (e.g. when :option:`iodepth_batch_complete` `=0`).
2442 .. option:: hipri_percentage : [pvsync2]
2444 When hipri is set this determines the probability of a pvsync2 I/O being high
2445 priority. The default is 100%.
2447 .. option:: nowait=bool : [pvsync2] [libaio] [io_uring] [io_uring_cmd]
2449 By default if a request cannot be executed immediately (e.g. resource starvation,
2450 waiting on locks) it is queued and the initiating process will be blocked until
2451 the required resource becomes free.
2453 This option sets the RWF_NOWAIT flag (supported from the 4.14 Linux kernel) and
2454 the call will return instantly with EAGAIN or a partial result rather than waiting.
2456 It is useful to also use ignore_error=EAGAIN when using this option.
2458 Note: glibc 2.27, 2.28 have a bug in syscall wrappers preadv2, pwritev2.
2459 They return EOPNOTSUP instead of EAGAIN.
2461 For cached I/O, using this option usually means a request operates only with
2462 cached data. Currently the RWF_NOWAIT flag does not supported for cached write.
2464 For direct I/O, requests will only succeed if cache invalidation isn't required,
2465 file blocks are fully allocated and the disk request could be issued immediately.
2467 .. option:: fdp=bool : [io_uring_cmd] [xnvme]
2469 Enable Flexible Data Placement mode for write commands.
2471 .. option:: fdp_pli_select=str : [io_uring_cmd] [xnvme]
2473 Defines how fio decides which placement ID to use next. The following
2477 Choose a placement ID at random (uniform).
2480 Round robin over available placement IDs. This is the
2483 The available placement ID index/indices is defined by the option
2486 .. option:: fdp_pli=str : [io_uring_cmd] [xnvme]
2488 Select which Placement ID Index/Indicies this job is allowed to use for
2489 writes. By default, the job will cycle through all available Placement
2490 IDs, so use this to isolate these identifiers to specific jobs. If you
2491 want fio to use placement identifier only at indices 0, 2 and 5 specify
2494 .. option:: md_per_io_size=int : [io_uring_cmd]
2496 Size in bytes for separate metadata buffer per IO. Default: 0.
2498 .. option:: pi_act=int : [io_uring_cmd]
2500 Action to take when nvme namespace is formatted with protection
2501 information. If this is set to 1 and namespace is formatted with
2502 metadata size equal to protection information size, fio won't use
2503 separate metadata buffer or extended logical block. If this is set to
2504 1 and namespace is formatted with metadata size greater than protection
2505 information size, fio will not generate or verify the protection
2506 information portion of metadata for write or read case respectively.
2507 If this is set to 0, fio generates protection information for
2508 write case and verifies for read case. Default: 1.
2510 .. option:: pi_chk=str[,str][,str] : [io_uring_cmd]
2512 Controls the protection information check. This can take one or more
2513 of these values. Default: none.
2516 Enables protection information checking of guard field.
2518 Enables protection information checking of logical block
2519 reference tag field.
2521 Enables protection information checking of application tag field.
2523 .. option:: apptag=int : [io_uring_cmd]
2525 Specifies logical block application tag value, if namespace is
2526 formatted to use end to end protection information. Default: 0x1234.
2528 .. option:: apptag_mask=int : [io_uring_cmd]
2530 Specifies logical block application tag mask value, if namespace is
2531 formatted to use end to end protection information. Default: 0xffff.
2533 .. option:: cpuload=int : [cpuio]
2535 Attempt to use the specified percentage of CPU cycles. This is a mandatory
2536 option when using cpuio I/O engine.
2538 .. option:: cpuchunks=int : [cpuio]
2540 Split the load into cycles of the given time. In microseconds.
2542 .. option:: cpumode=str : [cpuio]
2544 Specify how to stress the CPU. It can take these two values:
2547 This is the default where the CPU executes noop instructions.
2549 Replace the default noop instructions loop with a qsort algorithm to
2550 consume more energy.
2552 .. option:: exit_on_io_done=bool : [cpuio]
2554 Detect when I/O threads are done, then exit.
2556 .. option:: namenode=str : [libhdfs]
2558 The hostname or IP address of a HDFS cluster namenode to contact.
2560 .. option:: port=int
2564 The listening port of the HFDS cluster namenode.
2568 The TCP or UDP port to bind to or connect to. If this is used with
2569 :option:`numjobs` to spawn multiple instances of the same job type, then
2570 this will be the starting port number since fio will use a range of
2575 The port to use for RDMA-CM communication. This should be the same value
2576 on the client and the server side.
2578 .. option:: hostname=str : [netsplice] [net] [rdma]
2580 The hostname or IP address to use for TCP, UDP or RDMA-CM based I/O. If the job
2581 is a TCP listener or UDP reader, the hostname is not used and must be omitted
2582 unless it is a valid UDP multicast address.
2584 .. option:: serverip=str : [librpma_*]
2586 The IP address to be used for RDMA-CM based I/O.
2588 .. option:: direct_write_to_pmem=bool : [librpma_*]
2590 Set to 1 only when Direct Write to PMem from the remote host is possible.
2591 Otherwise, set to 0.
2593 .. option:: busy_wait_polling=bool : [librpma_*_server]
2595 Set to 0 to wait for completion instead of busy-wait polling completion.
2598 .. option:: interface=str : [netsplice] [net]
2600 The IP address of the network interface used to send or receive UDP
2603 .. option:: ttl=int : [netsplice] [net]
2605 Time-to-live value for outgoing UDP multicast packets. Default: 1.
2607 .. option:: nodelay=bool : [netsplice] [net]
2609 Set TCP_NODELAY on TCP connections.
2611 .. option:: protocol=str, proto=str : [netsplice] [net]
2613 The network protocol to use. Accepted values are:
2616 Transmission control protocol.
2618 Transmission control protocol V6.
2620 User datagram protocol.
2622 User datagram protocol V6.
2626 When the protocol is TCP or UDP, the port must also be given, as well as the
2627 hostname if the job is a TCP listener or UDP reader. For unix sockets, the
2628 normal :option:`filename` option should be used and the port is invalid.
2630 .. option:: listen : [netsplice] [net]
2632 For TCP network connections, tell fio to listen for incoming connections
2633 rather than initiating an outgoing connection. The :option:`hostname` must
2634 be omitted if this option is used.
2636 .. option:: pingpong : [netsplice] [net]
2638 Normally a network writer will just continue writing data, and a network
2639 reader will just consume packages. If ``pingpong=1`` is set, a writer will
2640 send its normal payload to the reader, then wait for the reader to send the
2641 same payload back. This allows fio to measure network latencies. The
2642 submission and completion latencies then measure local time spent sending or
2643 receiving, and the completion latency measures how long it took for the
2644 other end to receive and send back. For UDP multicast traffic
2645 ``pingpong=1`` should only be set for a single reader when multiple readers
2646 are listening to the same address.
2648 .. option:: window_size : [netsplice] [net]
2650 Set the desired socket buffer size for the connection.
2652 .. option:: mss : [netsplice] [net]
2654 Set the TCP maximum segment size (TCP_MAXSEG).
2656 .. option:: donorname=str : [e4defrag]
2658 File will be used as a block donor (swap extents between files).
2660 .. option:: inplace=int : [e4defrag]
2662 Configure donor file blocks allocation strategy:
2665 Default. Preallocate donor's file on init.
2667 Allocate space immediately inside defragment event, and free right
2670 .. option:: clustername=str : [rbd,rados]
2672 Specifies the name of the Ceph cluster.
2674 .. option:: rbdname=str : [rbd]
2676 Specifies the name of the RBD.
2678 .. option:: clientname=str : [rbd,rados]
2680 Specifies the username (without the 'client.' prefix) used to access the
2681 Ceph cluster. If the *clustername* is specified, the *clientname* shall be
2682 the full *type.id* string. If no type. prefix is given, fio will add
2683 'client.' by default.
2685 .. option:: conf=str : [rados]
2687 Specifies the configuration path of ceph cluster, so conf file does not
2688 have to be /etc/ceph/ceph.conf.
2690 .. option:: busy_poll=bool : [rbd,rados]
2692 Poll store instead of waiting for completion. Usually this provides better
2693 throughput at cost of higher(up to 100%) CPU utilization.
2695 .. option:: touch_objects=bool : [rados]
2697 During initialization, touch (create if do not exist) all objects (files).
2698 Touching all objects affects ceph caches and likely impacts test results.
2701 .. option:: pool=str :
2705 Specifies the name of the Ceph pool containing RBD or RADOS data.
2709 Specify the label or UUID of the DAOS pool to connect to.
2711 .. option:: cont=str : [dfs]
2713 Specify the label or UUID of the DAOS container to open.
2715 .. option:: chunk_size=int
2719 Specify a different chunk size (in bytes) for the dfs file.
2720 Use DAOS container's chunk size by default.
2724 The size of the chunk to use for each file.
2726 .. option:: object_class=str : [dfs]
2728 Specify a different object class for the dfs file.
2729 Use DAOS container's object class by default.
2731 .. option:: skip_bad=bool : [mtd]
2733 Skip operations against known bad blocks.
2735 .. option:: hdfsdirectory : [libhdfs]
2737 libhdfs will create chunk in this HDFS directory.
2739 .. option:: verb=str : [rdma]
2741 The RDMA verb to use on this side of the RDMA ioengine connection. Valid
2742 values are write, read, send and recv. These correspond to the equivalent
2743 RDMA verbs (e.g. write = rdma_write etc.). Note that this only needs to be
2744 specified on the client side of the connection. See the examples folder.
2746 .. option:: bindname=str : [rdma]
2748 The name to use to bind the local RDMA-CM connection to a local RDMA device.
2749 This could be a hostname or an IPv4 or IPv6 address. On the server side this
2750 will be passed into the rdma_bind_addr() function and on the client site it
2751 will be used in the rdma_resolve_add() function. This can be useful when
2752 multiple paths exist between the client and the server or in certain loopback
2755 .. option:: stat_type=str : [filestat]
2757 Specify stat system call type to measure lookup/getattr performance.
2758 Default is **stat** for :manpage:`stat(2)`.
2760 .. option:: readfua=bool : [sg]
2762 With readfua option set to 1, read operations include
2763 the force unit access (fua) flag. Default is 0.
2765 .. option:: writefua=bool : [sg]
2767 With writefua option set to 1, write operations include
2768 the force unit access (fua) flag. Default is 0.
2770 .. option:: sg_write_mode=str : [sg]
2772 Specify the type of write commands to issue. This option can take three values:
2775 This is the default where write opcodes are issued as usual.
2776 **write_and_verify**
2777 Issue WRITE AND VERIFY commands. The BYTCHK bit is set to 0. This
2778 directs the device to carry out a medium verification with no data
2779 comparison. The writefua option is ignored with this selection.
2781 This option is deprecated. Use write_and_verify instead.
2783 Issue WRITE SAME commands. This transfers a single block to the device
2784 and writes this same block of data to a contiguous sequence of LBAs
2785 beginning at the specified offset. fio's block size parameter specifies
2786 the amount of data written with each command. However, the amount of data
2787 actually transferred to the device is equal to the device's block
2788 (sector) size. For a device with 512 byte sectors, blocksize=8k will
2789 write 16 sectors with each command. fio will still generate 8k of data
2790 for each command but only the first 512 bytes will be used and
2791 transferred to the device. The writefua option is ignored with this
2794 This option is deprecated. Use write_same instead.
2796 Issue WRITE SAME(16) commands as above but with the No Data Output
2797 Buffer (NDOB) bit set. No data will be transferred to the device with
2798 this bit set. Data written will be a pre-determined pattern such as
2801 Issue WRITE STREAM(16) commands. Use the **stream_id** option to specify
2802 the stream identifier.
2803 **verify_bytchk_00**
2804 Issue VERIFY commands with BYTCHK set to 00. This directs the
2805 device to carry out a medium verification with no data comparison.
2806 **verify_bytchk_01**
2807 Issue VERIFY commands with BYTCHK set to 01. This directs the device to
2808 compare the data on the device with the data transferred to the device.
2809 **verify_bytchk_11**
2810 Issue VERIFY commands with BYTCHK set to 11. This transfers a
2811 single block to the device and compares the contents of this block with the
2812 data on the device beginning at the specified offset. fio's block size
2813 parameter specifies the total amount of data compared with this command.
2814 However, only one block (sector) worth of data is transferred to the device.
2815 This is similar to the WRITE SAME command except that data is compared instead
2818 .. option:: stream_id=int : [sg]
2820 Set the stream identifier for WRITE STREAM commands. If this is set to 0 (which is not
2821 a valid stream identifier) fio will open a stream and then close it when done. Default
2824 .. option:: http_host=str : [http]
2826 Hostname to connect to. For S3, this could be the bucket hostname.
2827 Default is **localhost**
2829 .. option:: http_user=str : [http]
2831 Username for HTTP authentication.
2833 .. option:: http_pass=str : [http]
2835 Password for HTTP authentication.
2837 .. option:: https=str : [http]
2839 Enable HTTPS instead of http. *on* enables HTTPS; *insecure*
2840 will enable HTTPS, but disable SSL peer verification (use with
2841 caution!). Default is **off**
2843 .. option:: http_mode=str : [http]
2845 Which HTTP access mode to use: *webdav*, *swift*, or *s3*.
2846 Default is **webdav**
2848 .. option:: http_s3_region=str : [http]
2850 The S3 region/zone string.
2851 Default is **us-east-1**
2853 .. option:: http_s3_key=str : [http]
2857 .. option:: http_s3_keyid=str : [http]
2859 The S3 key/access id.
2861 .. option:: http_s3_sse_customer_key=str : [http]
2863 The encryption customer key in SSE server side.
2865 .. option:: http_s3_sse_customer_algorithm=str : [http]
2867 The encryption customer algorithm in SSE server side.
2868 Default is **AES256**
2870 .. option:: http_s3_storage_class=str : [http]
2872 Which storage class to access. User-customizable settings.
2873 Default is **STANDARD**
2875 .. option:: http_swift_auth_token=str : [http]
2877 The Swift auth token. See the example configuration file on how
2880 .. option:: http_verbose=int : [http]
2882 Enable verbose requests from libcurl. Useful for debugging. 1
2883 turns on verbose logging from libcurl, 2 additionally enables
2884 HTTP IO tracing. Default is **0**
2886 .. option:: uri=str : [nbd]
2888 Specify the NBD URI of the server to test. The string
2889 is a standard NBD URI
2890 (see https://github.com/NetworkBlockDevice/nbd/tree/master/doc).
2891 Example URIs: nbd://localhost:10809
2892 nbd+unix:///?socket=/tmp/socket
2893 nbds://tlshost/exportname
2895 .. option:: gpu_dev_ids=str : [libcufile]
2897 Specify the GPU IDs to use with CUDA. This is a colon-separated list of
2898 int. GPUs are assigned to workers roundrobin. Default is 0.
2900 .. option:: cuda_io=str : [libcufile]
2902 Specify the type of I/O to use with CUDA. Default is **cufile**.
2905 Use libcufile and nvidia-fs. This option performs I/O directly
2906 between a GPUDirect Storage filesystem and GPU buffers,
2907 avoiding use of a bounce buffer. If :option:`verify` is set,
2908 cudaMemcpy is used to copy verificaton data between RAM and GPU.
2909 Verification data is copied from RAM to GPU before a write
2910 and from GPU to RAM after a read. :option:`direct` must be 1.
2912 Use POSIX to perform I/O with a RAM buffer, and use cudaMemcpy
2913 to transfer data between RAM and the GPUs. Data is copied from
2914 GPU to RAM before a write and copied from RAM to GPU after a
2915 read. :option:`verify` does not affect use of cudaMemcpy.
2917 .. option:: nfs_url=str : [nfs]
2919 URL in libnfs format, eg nfs://<server|ipv4|ipv6>/path[?arg=val[&arg=val]*]
2920 Refer to the libnfs README for more details.
2922 .. option:: program=str : [exec]
2924 Specify the program to execute.
2926 .. option:: arguments=str : [exec]
2928 Specify arguments to pass to program.
2929 Some special variables can be expanded to pass fio's job details to the program.
2932 Replaced by the duration of the job in seconds.
2934 Replaced by the name of the job.
2936 .. option:: grace_time=int : [exec]
2938 Specify the time between the SIGTERM and SIGKILL signals. Default is 1 second.
2940 .. option:: std_redirect=bool : [exec]
2942 If set, stdout and stderr streams are redirected to files named from the job name. Default is true.
2944 .. option:: xnvme_async=str : [xnvme]
2946 Select the xnvme async command interface. This can take these values.
2949 This is default and use to emulate asynchronous I/O by using a
2950 single thread to create a queue pair on top of a synchronous
2951 I/O interface using the NVMe driver IOCTL.
2953 Emulate an asynchronous I/O interface with a pool of userspace
2954 threads on top of a synchronous I/O interface using the NVMe
2955 driver IOCTL. By default four threads are used.
2957 Linux native asynchronous I/O interface which supports both
2958 direct and buffered I/O.
2960 Fast Linux native asynchronous I/O interface for NVMe pass
2961 through commands. This only works with NVMe character device
2964 Use Linux aio for Asynchronous I/O.
2966 Use the posix asynchronous I/O interface to perform one or
2967 more I/O operations asynchronously.
2969 Use the user-space VFIO-based backend, implemented using
2970 libvfn instead of SPDK.
2972 Do not transfer any data; just pretend to. This is mainly used
2973 for introspective performance evaluation.
2975 .. option:: xnvme_sync=str : [xnvme]
2977 Select the xnvme synchronous command interface. This can take these values.
2980 This is default and uses Linux NVMe Driver ioctl() for
2983 This supports regular as well as vectored pread() and pwrite()
2986 This is the same as psync except that it also supports zone
2987 management commands using Linux block layer IOCTLs.
2989 .. option:: xnvme_admin=str : [xnvme]
2991 Select the xnvme admin command interface. This can take these values.
2994 This is default and uses linux NVMe Driver ioctl() for admin
2997 Use Linux Block Layer ioctl() and sysfs for admin commands.
2999 .. option:: xnvme_dev_nsid=int : [xnvme]
3001 xnvme namespace identifier for userspace NVMe driver, SPDK or vfio.
3003 .. option:: xnvme_dev_subnqn=str : [xnvme]
3005 Sets the subsystem NQN for fabrics. This is for xNVMe to utilize a
3006 fabrics target with multiple systems.
3008 .. option:: xnvme_mem=str : [xnvme]
3010 Select the xnvme memory backend. This can take these values.
3013 This is the default posix memory backend for linux NVMe driver.
3015 Use hugepages, instead of existing posix memory backend. The
3016 memory backend uses hugetlbfs. This require users to allocate
3017 hugepages, mount hugetlbfs and set an enviornment variable for
3020 Uses SPDK's memory allocator.
3022 Uses libvfn's memory allocator. This also specifies the use
3023 of libvfn backend instead of SPDK.
3025 .. option:: xnvme_iovec=int : [xnvme]
3027 If this option is set. xnvme will use vectored read/write commands.
3029 .. option:: libblkio_driver=str : [libblkio]
3031 The libblkio *driver* to use. Different drivers access devices through
3032 different underlying interfaces. Available drivers depend on the
3033 libblkio version in use and are listed at
3034 https://libblkio.gitlab.io/libblkio/blkio.html#drivers
3036 .. option:: libblkio_path=str : [libblkio]
3038 Sets the value of the driver-specific "path" property before connecting
3039 the libblkio instance, which identifies the target device or file on
3040 which to perform I/O. Its exact semantics are driver-dependent and not
3041 all drivers may support it; see
3042 https://libblkio.gitlab.io/libblkio/blkio.html#drivers
3044 .. option:: libblkio_pre_connect_props=str : [libblkio]
3046 A colon-separated list of additional libblkio properties to be set after
3047 creating but before connecting the libblkio instance. Each property must
3048 have the format ``<name>=<value>``. Colons can be escaped as ``\:``.
3049 These are set after the engine sets any other properties, so those can
3050 be overriden. Available properties depend on the libblkio version in use
3052 https://libblkio.gitlab.io/libblkio/blkio.html#properties
3054 .. option:: libblkio_num_entries=int : [libblkio]
3056 Sets the value of the driver-specific "num-entries" property before
3057 starting the libblkio instance. Its exact semantics are driver-dependent
3058 and not all drivers may support it; see
3059 https://libblkio.gitlab.io/libblkio/blkio.html#drivers
3061 .. option:: libblkio_queue_size=int : [libblkio]
3063 Sets the value of the driver-specific "queue-size" property before
3064 starting the libblkio instance. Its exact semantics are driver-dependent
3065 and not all drivers may support it; see
3066 https://libblkio.gitlab.io/libblkio/blkio.html#drivers
3068 .. option:: libblkio_pre_start_props=str : [libblkio]
3070 A colon-separated list of additional libblkio properties to be set after
3071 connecting but before starting the libblkio instance. Each property must
3072 have the format ``<name>=<value>``. Colons can be escaped as ``\:``.
3073 These are set after the engine sets any other properties, so those can
3074 be overriden. Available properties depend on the libblkio version in use
3076 https://libblkio.gitlab.io/libblkio/blkio.html#properties
3078 .. option:: libblkio_vectored : [libblkio]
3080 Submit vectored read and write requests.
3082 .. option:: libblkio_write_zeroes_on_trim : [libblkio]
3084 Submit trims as "write zeroes" requests instead of discard requests.
3086 .. option:: libblkio_wait_mode=str : [libblkio]
3088 How to wait for completions:
3091 Use a blocking call to ``blkioq_do_io()``.
3093 Use a blocking call to ``read()`` on the completion eventfd.
3095 Use a busy loop with a non-blocking call to ``blkioq_do_io()``.
3097 .. option:: libblkio_force_enable_completion_eventfd : [libblkio]
3099 Enable the queue's completion eventfd even when unused. This may impact
3100 performance. The default is to enable it only if
3101 :option:`libblkio_wait_mode=eventfd <libblkio_wait_mode>`.
3103 .. option:: no_completion_thread : [windowsaio]
3105 Avoid using a separate thread for completion polling.
3110 .. option:: iodepth=int
3112 Number of I/O units to keep in flight against the file. Note that
3113 increasing *iodepth* beyond 1 will not affect synchronous ioengines (except
3114 for small degrees when :option:`verify_async` is in use). Even async
3115 engines may impose OS restrictions causing the desired depth not to be
3116 achieved. This may happen on Linux when using libaio and not setting
3117 :option:`direct`\=1, since buffered I/O is not async on that OS. Keep an
3118 eye on the I/O depth distribution in the fio output to verify that the
3119 achieved depth is as expected. Default: 1.
3121 .. option:: iodepth_batch_submit=int, iodepth_batch=int
3123 This defines how many pieces of I/O to submit at once. It defaults to 1
3124 which means that we submit each I/O as soon as it is available, but can be
3125 raised to submit bigger batches of I/O at the time. If it is set to 0 the
3126 :option:`iodepth` value will be used.
3128 .. option:: iodepth_batch_complete_min=int, iodepth_batch_complete=int
3130 This defines how many pieces of I/O to retrieve at once. It defaults to 1
3131 which means that we'll ask for a minimum of 1 I/O in the retrieval process
3132 from the kernel. The I/O retrieval will go on until we hit the limit set by
3133 :option:`iodepth_low`. If this variable is set to 0, then fio will always
3134 check for completed events before queuing more I/O. This helps reduce I/O
3135 latency, at the cost of more retrieval system calls.
3137 .. option:: iodepth_batch_complete_max=int
3139 This defines maximum pieces of I/O to retrieve at once. This variable should
3140 be used along with :option:`iodepth_batch_complete_min`\=int variable,
3141 specifying the range of min and max amount of I/O which should be
3142 retrieved. By default it is equal to the :option:`iodepth_batch_complete_min`
3147 iodepth_batch_complete_min=1
3148 iodepth_batch_complete_max=<iodepth>
3150 which means that we will retrieve at least 1 I/O and up to the whole
3151 submitted queue depth. If none of I/O has been completed yet, we will wait.
3155 iodepth_batch_complete_min=0
3156 iodepth_batch_complete_max=<iodepth>
3158 which means that we can retrieve up to the whole submitted queue depth, but
3159 if none of I/O has been completed yet, we will NOT wait and immediately exit
3160 the system call. In this example we simply do polling.
3162 .. option:: iodepth_low=int
3164 The low water mark indicating when to start filling the queue
3165 again. Defaults to the same as :option:`iodepth`, meaning that fio will
3166 attempt to keep the queue full at all times. If :option:`iodepth` is set to
3167 e.g. 16 and *iodepth_low* is set to 4, then after fio has filled the queue of
3168 16 requests, it will let the depth drain down to 4 before starting to fill
3171 .. option:: serialize_overlap=bool
3173 Serialize in-flight I/Os that might otherwise cause or suffer from data races.
3174 When two or more I/Os are submitted simultaneously, there is no guarantee that
3175 the I/Os will be processed or completed in the submitted order. Further, if
3176 two or more of those I/Os are writes, any overlapping region between them can
3177 become indeterminate/undefined on certain storage. These issues can cause
3178 verification to fail erratically when at least one of the racing I/Os is
3179 changing data and the overlapping region has a non-zero size. Setting
3180 ``serialize_overlap`` tells fio to avoid provoking this behavior by explicitly
3181 serializing in-flight I/Os that have a non-zero overlap. Note that setting
3182 this option can reduce both performance and the :option:`iodepth` achieved.
3184 This option only applies to I/Os issued for a single job except when it is
3185 enabled along with :option:`io_submit_mode`\=offload. In offload mode, fio
3186 will check for overlap among all I/Os submitted by offload jobs with :option:`serialize_overlap`
3191 .. option:: io_submit_mode=str
3193 This option controls how fio submits the I/O to the I/O engine. The default
3194 is `inline`, which means that the fio job threads submit and reap I/O
3195 directly. If set to `offload`, the job threads will offload I/O submission
3196 to a dedicated pool of I/O threads. This requires some coordination and thus
3197 has a bit of extra overhead, especially for lower queue depth I/O where it
3198 can increase latencies. The benefit is that fio can manage submission rates
3199 independently of the device completion rates. This avoids skewed latency
3200 reporting if I/O gets backed up on the device side (the coordinated omission
3201 problem). Note that this option cannot reliably be used with async IO
3208 .. option:: thinktime=time
3210 Stall the job for the specified period of time after an I/O has completed before issuing the
3211 next. May be used to simulate processing being done by an application.
3212 When the unit is omitted, the value is interpreted in microseconds. See
3213 :option:`thinktime_blocks`, :option:`thinktime_iotime` and :option:`thinktime_spin`.
3215 .. option:: thinktime_spin=time
3217 Only valid if :option:`thinktime` is set - pretend to spend CPU time doing
3218 something with the data received, before falling back to sleeping for the
3219 rest of the period specified by :option:`thinktime`. When the unit is
3220 omitted, the value is interpreted in microseconds.
3222 .. option:: thinktime_blocks=int
3224 Only valid if :option:`thinktime` is set - control how many blocks to issue,
3225 before waiting :option:`thinktime` usecs. If not set, defaults to 1 which will make
3226 fio wait :option:`thinktime` usecs after every block. This effectively makes any
3227 queue depth setting redundant, since no more than 1 I/O will be queued
3228 before we have to complete it and do our :option:`thinktime`. In other words, this
3229 setting effectively caps the queue depth if the latter is larger.
3231 .. option:: thinktime_blocks_type=str
3233 Only valid if :option:`thinktime` is set - control how :option:`thinktime_blocks`
3234 triggers. The default is `complete`, which triggers thinktime when fio completes
3235 :option:`thinktime_blocks` blocks. If this is set to `issue`, then the trigger happens
3238 .. option:: thinktime_iotime=time
3240 Only valid if :option:`thinktime` is set - control :option:`thinktime`
3241 interval by time. The :option:`thinktime` stall is repeated after IOs
3242 are executed for :option:`thinktime_iotime`. For example,
3243 ``--thinktime_iotime=9s --thinktime=1s`` repeat 10-second cycle with IOs
3244 for 9 seconds and stall for 1 second. When the unit is omitted,
3245 :option:`thinktime_iotime` is interpreted as a number of seconds. If
3246 this option is used together with :option:`thinktime_blocks`, the
3247 :option:`thinktime` stall is repeated after :option:`thinktime_iotime`
3248 or after :option:`thinktime_blocks` IOs, whichever happens first.
3250 .. option:: rate=int[,int][,int]
3252 Cap the bandwidth used by this job. The number is in bytes/sec, the normal
3253 suffix rules apply. Comma-separated values may be specified for reads,
3254 writes, and trims as described in :option:`blocksize`.
3256 For example, using `rate=1m,500k` would limit reads to 1MiB/sec and writes to
3257 500KiB/sec. Capping only reads or writes can be done with `rate=,500k` or
3258 `rate=500k,` where the former will only limit writes (to 500KiB/sec) and the
3259 latter will only limit reads.
3261 .. option:: rate_min=int[,int][,int]
3263 Tell fio to do whatever it can to maintain at least this bandwidth. Failing
3264 to meet this requirement will cause the job to exit. Comma-separated values
3265 may be specified for reads, writes, and trims as described in
3266 :option:`blocksize`.
3268 .. option:: rate_iops=int[,int][,int]
3270 Cap the bandwidth to this number of IOPS. Basically the same as
3271 :option:`rate`, just specified independently of bandwidth. If the job is
3272 given a block size range instead of a fixed value, the smallest block size
3273 is used as the metric. Comma-separated values may be specified for reads,
3274 writes, and trims as described in :option:`blocksize`.
3276 .. option:: rate_iops_min=int[,int][,int]
3278 If fio doesn't meet this rate of I/O, it will cause the job to exit.
3279 Comma-separated values may be specified for reads, writes, and trims as
3280 described in :option:`blocksize`.
3282 .. option:: rate_process=str
3284 This option controls how fio manages rated I/O submissions. The default is
3285 `linear`, which submits I/O in a linear fashion with fixed delays between
3286 I/Os that gets adjusted based on I/O completion rates. If this is set to
3287 `poisson`, fio will submit I/O based on a more real world random request
3288 flow, known as the Poisson process
3289 (https://en.wikipedia.org/wiki/Poisson_point_process). The lambda will be
3290 10^6 / IOPS for the given workload.
3292 .. option:: rate_ignore_thinktime=bool
3294 By default, fio will attempt to catch up to the specified rate setting,
3295 if any kind of thinktime setting was used. If this option is set, then
3296 fio will ignore the thinktime and continue doing IO at the specified
3297 rate, instead of entering a catch-up mode after thinktime is done.
3299 .. option:: rate_cycle=int
3301 Average bandwidth for :option:`rate` and :option:`rate_min` over this number
3302 of milliseconds. Defaults to 1000.
3308 .. option:: latency_target=time
3310 If set, fio will attempt to find the max performance point that the given
3311 workload will run at while maintaining a latency below this target. When
3312 the unit is omitted, the value is interpreted in microseconds. See
3313 :option:`latency_window` and :option:`latency_percentile`.
3315 .. option:: latency_window=time
3317 Used with :option:`latency_target` to specify the sample window that the job
3318 is run at varying queue depths to test the performance. When the unit is
3319 omitted, the value is interpreted in microseconds.
3321 .. option:: latency_percentile=float
3323 The percentage of I/Os that must fall within the criteria specified by
3324 :option:`latency_target` and :option:`latency_window`. If not set, this
3325 defaults to 100.0, meaning that all I/Os must be equal or below to the value
3326 set by :option:`latency_target`.
3328 .. option:: latency_run=bool
3330 Used with :option:`latency_target`. If false (default), fio will find
3331 the highest queue depth that meets :option:`latency_target` and exit. If
3332 true, fio will continue running and try to meet :option:`latency_target`
3333 by adjusting queue depth.
3335 .. option:: max_latency=time[,time][,time]
3337 If set, fio will exit the job with an ETIMEDOUT error if it exceeds this
3338 maximum latency. When the unit is omitted, the value is interpreted in
3339 microseconds. Comma-separated values may be specified for reads, writes,
3340 and trims as described in :option:`blocksize`.
3346 .. option:: write_iolog=str
3348 Write the issued I/O patterns to the specified file. See
3349 :option:`read_iolog`. Specify a separate file for each job, otherwise the
3350 iologs will be interspersed and the file may be corrupt. This file will
3351 be opened in append mode.
3353 .. option:: read_iolog=str
3355 Open an iolog with the specified filename and replay the I/O patterns it
3356 contains. This can be used to store a workload and replay it sometime
3357 later. The iolog given may also be a blktrace binary file, which allows fio
3358 to replay a workload captured by :command:`blktrace`. See
3359 :manpage:`blktrace(8)` for how to capture such logging data. For blktrace
3360 replay, the file needs to be turned into a blkparse binary data file first
3361 (``blkparse <device> -o /dev/null -d file_for_fio.bin``).
3362 You can specify a number of files by separating the names with a ':'
3363 character. See the :option:`filename` option for information on how to
3364 escape ':' characters within the file names. These files will
3365 be sequentially assigned to job clones created by :option:`numjobs`.
3366 '-' is a reserved name, meaning read from stdin, notably if
3367 :option:`filename` is set to '-' which means stdin as well, then
3368 this flag can't be set to '-'.
3370 .. option:: read_iolog_chunked=bool
3372 Determines how iolog is read. If false(default) entire :option:`read_iolog`
3373 will be read at once. If selected true, input from iolog will be read
3374 gradually. Useful when iolog is very large, or it is generated.
3376 .. option:: merge_blktrace_file=str
3378 When specified, rather than replaying the logs passed to :option:`read_iolog`,
3379 the logs go through a merge phase which aggregates them into a single
3380 blktrace. The resulting file is then passed on as the :option:`read_iolog`
3381 parameter. The intention here is to make the order of events consistent.
3382 This limits the influence of the scheduler compared to replaying multiple
3383 blktraces via concurrent jobs.
3385 .. option:: merge_blktrace_scalars=float_list
3387 This is a percentage based option that is index paired with the list of
3388 files passed to :option:`read_iolog`. When merging is performed, scale
3389 the time of each event by the corresponding amount. For example,
3390 ``--merge_blktrace_scalars="50:100"`` runs the first trace in halftime
3391 and the second trace in realtime. This knob is separately tunable from
3392 :option:`replay_time_scale` which scales the trace during runtime and
3393 does not change the output of the merge unlike this option.
3395 .. option:: merge_blktrace_iters=float_list
3397 This is a whole number option that is index paired with the list of files
3398 passed to :option:`read_iolog`. When merging is performed, run each trace
3399 for the specified number of iterations. For example,
3400 ``--merge_blktrace_iters="2:1"`` runs the first trace for two iterations
3401 and the second trace for one iteration.
3403 .. option:: replay_no_stall=bool
3405 When replaying I/O with :option:`read_iolog` the default behavior is to
3406 attempt to respect the timestamps within the log and replay them with the
3407 appropriate delay between IOPS. By setting this variable fio will not
3408 respect the timestamps and attempt to replay them as fast as possible while
3409 still respecting ordering. The result is the same I/O pattern to a given
3410 device, but different timings.
3412 .. option:: replay_time_scale=int
3414 When replaying I/O with :option:`read_iolog`, fio will honor the
3415 original timing in the trace. With this option, it's possible to scale
3416 the time. It's a percentage option, if set to 50 it means run at 50%
3417 the original IO rate in the trace. If set to 200, run at twice the
3418 original IO rate. Defaults to 100.
3420 .. option:: replay_redirect=str
3422 While replaying I/O patterns using :option:`read_iolog` the default behavior
3423 is to replay the IOPS onto the major/minor device that each IOP was recorded
3424 from. This is sometimes undesirable because on a different machine those
3425 major/minor numbers can map to a different device. Changing hardware on the
3426 same system can also result in a different major/minor mapping.
3427 ``replay_redirect`` causes all I/Os to be replayed onto the single specified
3428 device regardless of the device it was recorded
3429 from. i.e. :option:`replay_redirect`\= :file:`/dev/sdc` would cause all I/O
3430 in the blktrace or iolog to be replayed onto :file:`/dev/sdc`. This means
3431 multiple devices will be replayed onto a single device, if the trace
3432 contains multiple devices. If you want multiple devices to be replayed
3433 concurrently to multiple redirected devices you must blkparse your trace
3434 into separate traces and replay them with independent fio invocations.
3435 Unfortunately this also breaks the strict time ordering between multiple
3438 .. option:: replay_align=int
3440 Force alignment of the byte offsets in a trace to this value. The value
3441 must be a power of 2.
3443 .. option:: replay_scale=int
3445 Scale byte offsets down by this factor when replaying traces. Should most
3446 likely use :option:`replay_align` as well.
3448 .. option:: replay_skip=str
3450 Sometimes it's useful to skip certain IO types in a replay trace.
3451 This could be, for instance, eliminating the writes in the trace.
3452 Or not replaying the trims/discards, if you are redirecting to
3453 a device that doesn't support them. This option takes a comma
3454 separated list of read, write, trim, sync.
3457 Threads, processes and job synchronization
3458 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
3462 Fio defaults to creating jobs by using fork, however if this option is
3463 given, fio will create jobs by using POSIX Threads' function
3464 :manpage:`pthread_create(3)` to create threads instead.
3466 .. option:: wait_for=str
3468 If set, the current job won't be started until all workers of the specified
3469 waitee job are done.
3471 ``wait_for`` operates on the job name basis, so there are a few
3472 limitations. First, the waitee must be defined prior to the waiter job
3473 (meaning no forward references). Second, if a job is being referenced as a
3474 waitee, it must have a unique name (no duplicate waitees).
3476 .. option:: nice=int
3478 Run the job with the given nice value. See man :manpage:`nice(2)`.
3480 On Windows, values less than -15 set the process class to "High"; -1 through
3481 -15 set "Above Normal"; 1 through 15 "Below Normal"; and above 15 "Idle"
3484 .. option:: prio=int
3486 Set the I/O priority value of this job. Linux limits us to a positive value
3487 between 0 and 7, with 0 being the highest. See man
3488 :manpage:`ionice(1)`. Refer to an appropriate manpage for other operating
3489 systems since meaning of priority may differ. For per-command priority
3490 setting, see I/O engine specific :option:`cmdprio_percentage` and
3491 :option:`cmdprio` options.
3493 .. option:: prioclass=int
3495 Set the I/O priority class. See man :manpage:`ionice(1)`. For per-command
3496 priority setting, see I/O engine specific :option:`cmdprio_percentage`
3497 and :option:`cmdprio_class` options.
3499 .. option:: priohint=int
3501 Set the I/O priority hint. This is only applicable to platforms that
3502 support I/O priority classes and to devices with features controlled
3503 through priority hints, e.g. block devices supporting command duration
3504 limits, or CDL. CDL is a way to indicate the desired maximum latency
3505 of I/Os so that the device can optimize its internal command scheduling
3506 according to the latency limits indicated by the user.
3508 For per-I/O priority hint setting, see the I/O engine specific
3509 :option:`cmdprio_hint` option.
3511 .. option:: cpus_allowed=str
3513 Controls the same options as :option:`cpumask`, but accepts a textual
3514 specification of the permitted CPUs instead and CPUs are indexed from 0. So
3515 to use CPUs 0 and 5 you would specify ``cpus_allowed=0,5``. This option also
3516 allows a range of CPUs to be specified -- say you wanted a binding to CPUs
3517 0, 5, and 8 to 15, you would set ``cpus_allowed=0,5,8-15``.
3519 On Windows, when ``cpus_allowed`` is unset only CPUs from fio's current
3520 processor group will be used and affinity settings are inherited from the
3521 system. An fio build configured to target Windows 7 makes options that set
3522 CPUs processor group aware and values will set both the processor group
3523 and a CPU from within that group. For example, on a system where processor
3524 group 0 has 40 CPUs and processor group 1 has 32 CPUs, ``cpus_allowed``
3525 values between 0 and 39 will bind CPUs from processor group 0 and
3526 ``cpus_allowed`` values between 40 and 71 will bind CPUs from processor
3527 group 1. When using ``cpus_allowed_policy=shared`` all CPUs specified by a
3528 single ``cpus_allowed`` option must be from the same processor group. For
3529 Windows fio builds not built for Windows 7, CPUs will only be selected from
3530 (and be relative to) whatever processor group fio happens to be running in
3531 and CPUs from other processor groups cannot be used.
3533 .. option:: cpus_allowed_policy=str
3535 Set the policy of how fio distributes the CPUs specified by
3536 :option:`cpus_allowed` or :option:`cpumask`. Two policies are supported:
3539 All jobs will share the CPU set specified.
3541 Each job will get a unique CPU from the CPU set.
3543 **shared** is the default behavior, if the option isn't specified. If
3544 **split** is specified, then fio will assign one cpu per job. If not
3545 enough CPUs are given for the jobs listed, then fio will roundrobin the CPUs
3548 .. option:: cpumask=int
3550 Set the CPU affinity of this job. The parameter given is a bit mask of
3551 allowed CPUs the job may run on. So if you want the allowed CPUs to be 1
3552 and 5, you would pass the decimal value of (1 << 1 | 1 << 5), or 34. See man
3553 :manpage:`sched_setaffinity(2)`. This may not work on all supported
3554 operating systems or kernel versions. This option doesn't work well for a
3555 higher CPU count than what you can store in an integer mask, so it can only
3556 control cpus 1-32. For boxes with larger CPU counts, use
3557 :option:`cpus_allowed`.
3559 .. option:: numa_cpu_nodes=str
3561 Set this job running on specified NUMA nodes' CPUs. The arguments allow
3562 comma delimited list of cpu numbers, A-B ranges, or `all`. Note, to enable
3563 NUMA options support, fio must be built on a system with libnuma-dev(el)
3566 .. option:: numa_mem_policy=str
3568 Set this job's memory policy and corresponding NUMA nodes. Format of the
3573 ``mode`` is one of the following memory policies: ``default``, ``prefer``,
3574 ``bind``, ``interleave`` or ``local``. For ``default`` and ``local`` memory
3575 policies, no node needs to be specified. For ``prefer``, only one node is
3576 allowed. For ``bind`` and ``interleave`` the ``nodelist`` may be as
3577 follows: a comma delimited list of numbers, A-B ranges, or `all`.
3579 .. option:: cgroup=str
3581 Add job to this control group. If it doesn't exist, it will be created. The
3582 system must have a mounted cgroup blkio mount point for this to work. If
3583 your system doesn't have it mounted, you can do so with::
3585 # mount -t cgroup -o blkio none /cgroup
3587 .. option:: cgroup_weight=int
3589 Set the weight of the cgroup to this value. See the documentation that comes
3590 with the kernel, allowed values are in the range of 100..1000.
3592 .. option:: cgroup_nodelete=bool
3594 Normally fio will delete the cgroups it has created after the job
3595 completion. To override this behavior and to leave cgroups around after the
3596 job completion, set ``cgroup_nodelete=1``. This can be useful if one wants
3597 to inspect various cgroup files after job completion. Default: false.
3599 .. option:: flow_id=int
3601 The ID of the flow. If not specified, it defaults to being a global
3602 flow. See :option:`flow`.
3604 .. option:: flow=int
3606 Weight in token-based flow control. If this value is used, then fio
3607 regulates the activity between two or more jobs sharing the same
3608 flow_id. Fio attempts to keep each job activity proportional to other
3609 jobs' activities in the same flow_id group, with respect to requested
3610 weight per job. That is, if one job has `flow=3', another job has
3611 `flow=2' and another with `flow=1`, then there will be a roughly 3:2:1
3612 ratio in how much one runs vs the others.
3614 .. option:: flow_sleep=int
3616 The period of time, in microseconds, to wait after the flow counter
3617 has exceeded its proportion before retrying operations.
3619 .. option:: stonewall, wait_for_previous
3621 Wait for preceding jobs in the job file to exit, before starting this
3622 one. Can be used to insert serialization points in the job file. A stone
3623 wall also implies starting a new reporting group, see
3624 :option:`group_reporting`.
3628 By default, fio will continue running all other jobs when one job finishes.
3629 Sometimes this is not the desired action. Setting ``exitall`` will instead
3630 make fio terminate all jobs in the same group, as soon as one job of that
3633 .. option:: exit_what=str
3635 By default, fio will continue running all other jobs when one job finishes.
3636 Sometimes this is not the desired action. Setting ``exitall`` will
3637 instead make fio terminate all jobs in the same group. The option
3638 ``exit_what`` allows to control which jobs get terminated when ``exitall`` is
3639 enabled. The default is ``group`` and does not change the behaviour of
3640 ``exitall``. The setting ``all`` terminates all jobs. The setting ``stonewall``
3641 terminates all currently running jobs across all groups and continues execution
3642 with the next stonewalled group.
3644 .. option:: exec_prerun=str
3646 Before running this job, issue the command specified through
3647 :manpage:`system(3)`. Output is redirected in a file called
3648 :file:`jobname.prerun.txt`.
3650 .. option:: exec_postrun=str
3652 After the job completes, issue the command specified though
3653 :manpage:`system(3)`. Output is redirected in a file called
3654 :file:`jobname.postrun.txt`.
3658 Instead of running as the invoking user, set the user ID to this value
3659 before the thread/process does any work.
3663 Set group ID, see :option:`uid`.
3669 .. option:: verify_only
3671 Do not perform specified workload, only verify data still matches previous
3672 invocation of this workload. This option allows one to check data multiple
3673 times at a later date without overwriting it. This option makes sense only
3674 for workloads that write data, and does not support workloads with the
3675 :option:`time_based` option set.
3677 .. option:: do_verify=bool
3679 Run the verify phase after a write phase. Only valid if :option:`verify` is
3682 .. option:: verify=str
3684 If writing to a file, fio can verify the file contents after each iteration
3685 of the job. Each verification method also implies verification of special
3686 header, which is written to the beginning of each block. This header also
3687 includes meta information, like offset of the block, block number, timestamp
3688 when block was written, etc. :option:`verify` can be combined with
3689 :option:`verify_pattern` option. The allowed values are:
3692 Use an md5 sum of the data area and store it in the header of
3696 Use an experimental crc64 sum of the data area and store it in the
3697 header of each block.
3700 Use a crc32c sum of the data area and store it in the header of
3701 each block. This will automatically use hardware acceleration
3702 (e.g. SSE4.2 on an x86 or CRC crypto extensions on ARM64) but will
3703 fall back to software crc32c if none is found. Generally the
3704 fastest checksum fio supports when hardware accelerated.
3710 Use a crc32 sum of the data area and store it in the header of each
3714 Use a crc16 sum of the data area and store it in the header of each
3718 Use a crc7 sum of the data area and store it in the header of each
3722 Use xxhash as the checksum function. Generally the fastest software
3723 checksum that fio supports.
3726 Use sha512 as the checksum function.
3729 Use sha256 as the checksum function.
3732 Use optimized sha1 as the checksum function.
3735 Use optimized sha3-224 as the checksum function.
3738 Use optimized sha3-256 as the checksum function.
3741 Use optimized sha3-384 as the checksum function.
3744 Use optimized sha3-512 as the checksum function.
3747 This option is deprecated, since now meta information is included in
3748 generic verification header and meta verification happens by
3749 default. For detailed information see the description of the
3750 :option:`verify` setting. This option is kept because of
3751 compatibility's sake with old configurations. Do not use it.
3754 Verify a strict pattern. Normally fio includes a header with some
3755 basic information and checksumming, but if this option is set, only
3756 the specific pattern set with :option:`verify_pattern` is verified.
3759 Only pretend to verify. Useful for testing internals with
3760 :option:`ioengine`\=null, not for much else.
3762 This option can be used for repeated burn-in tests of a system to make sure
3763 that the written data is also correctly read back. If the data direction
3764 given is a read or random read, fio will assume that it should verify a
3765 previously written file. If the data direction includes any form of write,
3766 the verify will be of the newly written data.
3768 To avoid false verification errors, do not use the norandommap option when
3769 verifying data with async I/O engines and I/O depths > 1. Or use the
3770 norandommap and the lfsr random generator together to avoid writing to the
3771 same offset with multiple outstanding I/Os.
3773 .. option:: verify_offset=int
3775 Swap the verification header with data somewhere else in the block before
3776 writing. It is swapped back before verifying.
3778 .. option:: verify_interval=int
3780 Write the verification header at a finer granularity than the
3781 :option:`blocksize`. It will be written for chunks the size of
3782 ``verify_interval``. :option:`blocksize` should divide this evenly.
3784 .. option:: verify_pattern=str
3786 If set, fio will fill the I/O buffers with this pattern. Fio defaults to
3787 filling with totally random bytes, but sometimes it's interesting to fill
3788 with a known pattern for I/O verification purposes. Depending on the width
3789 of the pattern, fio will fill 1/2/3/4 bytes of the buffer at the time (it can
3790 be either a decimal or a hex number). The ``verify_pattern`` if larger than
3791 a 32-bit quantity has to be a hex number that starts with either "0x" or
3792 "0X". Use with :option:`verify`. Also, ``verify_pattern`` supports %o
3793 format, which means that for each block offset will be written and then
3794 verified back, e.g.::
3798 Or use combination of everything::
3800 verify_pattern=0xff%o"abcd"-12
3802 .. option:: verify_fatal=bool
3804 Normally fio will keep checking the entire contents before quitting on a
3805 block verification failure. If this option is set, fio will exit the job on
3806 the first observed failure. Default: false.
3808 .. option:: verify_dump=bool
3810 If set, dump the contents of both the original data block and the data block
3811 we read off disk to files. This allows later analysis to inspect just what
3812 kind of data corruption occurred. Off by default.
3814 .. option:: verify_async=int
3816 Fio will normally verify I/O inline from the submitting thread. This option
3817 takes an integer describing how many async offload threads to create for I/O
3818 verification instead, causing fio to offload the duty of verifying I/O
3819 contents to one or more separate threads. If using this offload option, even
3820 sync I/O engines can benefit from using an :option:`iodepth` setting higher
3821 than 1, as it allows them to have I/O in flight while verifies are running.
3822 Defaults to 0 async threads, i.e. verification is not asynchronous.
3824 .. option:: verify_async_cpus=str
3826 Tell fio to set the given CPU affinity on the async I/O verification
3827 threads. See :option:`cpus_allowed` for the format used.
3829 .. option:: verify_backlog=int
3831 Fio will normally verify the written contents of a job that utilizes verify
3832 once that job has completed. In other words, everything is written then
3833 everything is read back and verified. You may want to verify continually
3834 instead for a variety of reasons. Fio stores the meta data associated with
3835 an I/O block in memory, so for large verify workloads, quite a bit of memory
3836 would be used up holding this meta data. If this option is enabled, fio will
3837 write only N blocks before verifying these blocks.
3839 .. option:: verify_backlog_batch=int
3841 Control how many blocks fio will verify if :option:`verify_backlog` is
3842 set. If not set, will default to the value of :option:`verify_backlog`
3843 (meaning the entire queue is read back and verified). If
3844 ``verify_backlog_batch`` is less than :option:`verify_backlog` then not all
3845 blocks will be verified, if ``verify_backlog_batch`` is larger than
3846 :option:`verify_backlog`, some blocks will be verified more than once.
3848 .. option:: verify_state_save=bool
3850 When a job exits during the write phase of a verify workload, save its
3851 current state. This allows fio to replay up until that point, if the verify
3852 state is loaded for the verify read phase. The format of the filename is,
3855 <type>-<jobname>-<jobindex>-verify.state.
3857 <type> is "local" for a local run, "sock" for a client/server socket
3858 connection, and "ip" (192.168.0.1, for instance) for a networked
3859 client/server connection. Defaults to true.
3861 .. option:: verify_state_load=bool
3863 If a verify termination trigger was used, fio stores the current write state
3864 of each thread. This can be used at verification time so that fio knows how
3865 far it should verify. Without this information, fio will run a full
3866 verification pass, according to the settings in the job file used. Default
3869 .. option:: experimental_verify=bool
3871 Enable experimental verification. Standard verify records I/O metadata
3872 for later use during the verification phase. Experimental verify
3873 instead resets the file after the write phase and then replays I/Os for
3874 the verification phase.
3876 .. option:: trim_percentage=int
3878 Number of verify blocks to discard/trim.
3880 .. option:: trim_verify_zero=bool
3882 Verify that trim/discarded blocks are returned as zeros.
3884 .. option:: trim_backlog=int
3886 Trim after this number of blocks are written.
3888 .. option:: trim_backlog_batch=int
3890 Trim this number of I/O blocks.
3895 .. option:: steadystate=str:float, ss=str:float
3897 Define the criterion and limit for assessing steady state performance. The
3898 first parameter designates the criterion whereas the second parameter sets
3899 the threshold. When the criterion falls below the threshold for the
3900 specified duration, the job will stop. For example, `iops_slope:0.1%` will
3901 direct fio to terminate the job when the least squares regression slope
3902 falls below 0.1% of the mean IOPS. If :option:`group_reporting` is enabled
3903 this will apply to all jobs in the group. Below is the list of available
3904 steady state assessment criteria. All assessments are carried out using only
3905 data from the rolling collection window. Threshold limits can be expressed
3906 as a fixed value or as a percentage of the mean in the collection window.
3908 When using this feature, most jobs should include the :option:`time_based`
3909 and :option:`runtime` options or the :option:`loops` option so that fio does not
3910 stop running after it has covered the full size of the specified file(s) or device(s).
3913 Collect IOPS data. Stop the job if all individual IOPS measurements
3914 are within the specified limit of the mean IOPS (e.g., ``iops:2``
3915 means that all individual IOPS values must be within 2 of the mean,
3916 whereas ``iops:0.2%`` means that all individual IOPS values must be
3917 within 0.2% of the mean IOPS to terminate the job).
3920 Collect IOPS data and calculate the least squares regression
3921 slope. Stop the job if the slope falls below the specified limit.
3924 Collect bandwidth data. Stop the job if all individual bandwidth
3925 measurements are within the specified limit of the mean bandwidth.
3928 Collect bandwidth data and calculate the least squares regression
3929 slope. Stop the job if the slope falls below the specified limit.
3931 .. option:: steadystate_duration=time, ss_dur=time
3933 A rolling window of this duration will be used to judge whether steady
3934 state has been reached. Data will be collected every
3935 :option:`ss_interval`. The default is 0 which disables steady state
3936 detection. When the unit is omitted, the value is interpreted in
3939 .. option:: steadystate_ramp_time=time, ss_ramp=time
3941 Allow the job to run for the specified duration before beginning data
3942 collection for checking the steady state job termination criterion. The
3943 default is 0. When the unit is omitted, the value is interpreted in seconds.
3945 .. option:: steadystate_check_interval=time, ss_interval=time
3947 The values during the rolling window will be collected with a period of
3948 this value. If :option:`ss_interval` is 30s and :option:`ss_dur` is
3949 300s, 10 measurements will be taken. Default is 1s but that might not
3950 converge, especially for slower devices, so set this accordingly. When
3951 the unit is omitted, the value is interpreted in seconds.
3954 Measurements and reporting
3955 ~~~~~~~~~~~~~~~~~~~~~~~~~~
3957 .. option:: per_job_logs=bool
3959 If set, this generates bw/clat/iops log with per file private filenames. If
3960 not set, jobs with identical names will share the log filename. Default:
3963 .. option:: group_reporting
3965 It may sometimes be interesting to display statistics for groups of jobs as
3966 a whole instead of for each individual job. This is especially true if
3967 :option:`numjobs` is used; looking at individual thread/process output
3968 quickly becomes unwieldy. To see the final report per-group instead of
3969 per-job, use :option:`group_reporting`. Jobs in a file will be part of the
3970 same reporting group, unless if separated by a :option:`stonewall`, or by
3971 using :option:`new_group`.
3973 NOTE: When :option: `group_reporting` is used along with `json` output,
3974 there are certain per-job properties which can be different between jobs
3975 but do not have a natural group-level equivalent. Examples include
3976 `kb_base`, `unit_base`, `sig_figs`, `thread_number`, `pid`, and
3977 `job_start`. For these properties, the values for the first job are
3978 recorded for the group.
3980 .. option:: new_group
3982 Start a new reporting group. See: :option:`group_reporting`. If not given,
3983 all jobs in a file will be part of the same reporting group, unless
3984 separated by a :option:`stonewall`.
3986 .. option:: stats=bool
3988 By default, fio collects and shows final output results for all jobs
3989 that run. If this option is set to 0, then fio will ignore it in
3990 the final stat output.
3992 .. option:: write_bw_log=str
3994 If given, write a bandwidth log for this job. Can be used to store data of
3995 the bandwidth of the jobs in their lifetime.
3997 If no str argument is given, the default filename of
3998 :file:`jobname_type.x.log` is used. Even when the argument is given, fio
3999 will still append the type of log. So if one specifies::
4003 The actual log name will be :file:`foo_bw.x.log` where `x` is the index
4004 of the job (`1..N`, where `N` is the number of jobs). If
4005 :option:`per_job_logs` is false, then the filename will not include the
4008 The included :command:`fio_generate_plots` script uses :command:`gnuplot` to turn these
4009 text files into nice graphs. See `Log File Formats`_ for how data is
4010 structured within the file.
4012 .. option:: write_lat_log=str
4014 Same as :option:`write_bw_log`, except this option creates I/O
4015 submission (e.g., :file:`name_slat.x.log`), completion (e.g.,
4016 :file:`name_clat.x.log`), and total (e.g., :file:`name_lat.x.log`)
4017 latency files instead. See :option:`write_bw_log` for details about
4018 the filename format and `Log File Formats`_ for how data is structured
4021 .. option:: write_hist_log=str
4023 Same as :option:`write_bw_log` but writes an I/O completion latency
4024 histogram file (e.g., :file:`name_hist.x.log`) instead. Note that this
4025 file will be empty unless :option:`log_hist_msec` has also been set.
4026 See :option:`write_bw_log` for details about the filename format and
4027 `Log File Formats`_ for how data is structured within the file.
4029 .. option:: write_iops_log=str
4031 Same as :option:`write_bw_log`, but writes an IOPS file (e.g.
4032 :file:`name_iops.x.log`) instead. Because fio defaults to individual
4033 I/O logging, the value entry in the IOPS log will be 1 unless windowed
4034 logging (see :option:`log_avg_msec`) has been enabled. See
4035 :option:`write_bw_log` for details about the filename format and `Log
4036 File Formats`_ for how data is structured within the file.
4038 .. option:: log_entries=int
4040 By default, fio will log an entry in the iops, latency, or bw log for
4041 every I/O that completes. The initial number of I/O log entries is 1024.
4042 When the log entries are all used, new log entries are dynamically
4043 allocated. This dynamic log entry allocation may negatively impact
4044 time-related statistics such as I/O tail latencies (e.g. 99.9th percentile
4045 completion latency). This option allows specifying a larger initial
4046 number of log entries to avoid run-time allocations of new log entries,
4047 resulting in more precise time-related I/O statistics.
4048 Also see :option:`log_avg_msec`. Defaults to 1024.
4050 .. option:: log_avg_msec=int
4052 By default, fio will log an entry in the iops, latency, or bw log for every
4053 I/O that completes. When writing to the disk log, that can quickly grow to a
4054 very large size. Setting this option makes fio average the each log entry
4055 over the specified period of time, reducing the resolution of the log. See
4056 :option:`log_max_value` as well. Defaults to 0, logging all entries.
4057 Also see `Log File Formats`_.
4059 .. option:: log_hist_msec=int
4061 Same as :option:`log_avg_msec`, but logs entries for completion latency
4062 histograms. Computing latency percentiles from averages of intervals using
4063 :option:`log_avg_msec` is inaccurate. Setting this option makes fio log
4064 histogram entries over the specified period of time, reducing log sizes for
4065 high IOPS devices while retaining percentile accuracy. See
4066 :option:`log_hist_coarseness` and :option:`write_hist_log` as well.
4067 Defaults to 0, meaning histogram logging is disabled.
4069 .. option:: log_hist_coarseness=int
4071 Integer ranging from 0 to 6, defining the coarseness of the resolution of
4072 the histogram logs enabled with :option:`log_hist_msec`. For each increment
4073 in coarseness, fio outputs half as many bins. Defaults to 0, for which
4074 histogram logs contain 1216 latency bins. See :option:`write_hist_log`
4075 and `Log File Formats`_.
4077 .. option:: log_max_value=bool
4079 If :option:`log_avg_msec` is set, fio logs the average over that window. If
4080 you instead want to log the maximum value, set this option to 1. Defaults to
4081 0, meaning that averaged values are logged.
4083 .. option:: log_offset=bool
4085 If this is set, the iolog options will include the byte offset for the I/O
4086 entry as well as the other data values. Defaults to 0 meaning that
4087 offsets are not present in logs. Also see `Log File Formats`_.
4089 .. option:: log_compression=int
4091 If this is set, fio will compress the I/O logs as it goes, to keep the
4092 memory footprint lower. When a log reaches the specified size, that chunk is
4093 removed and compressed in the background. Given that I/O logs are fairly
4094 highly compressible, this yields a nice memory savings for longer runs. The
4095 downside is that the compression will consume some background CPU cycles, so
4096 it may impact the run. This, however, is also true if the logging ends up
4097 consuming most of the system memory. So pick your poison. The I/O logs are
4098 saved normally at the end of a run, by decompressing the chunks and storing
4099 them in the specified log file. This feature depends on the availability of
4102 .. option:: log_compression_cpus=str
4104 Define the set of CPUs that are allowed to handle online log compression for
4105 the I/O jobs. This can provide better isolation between performance
4106 sensitive jobs, and background compression work. See
4107 :option:`cpus_allowed` for the format used.
4109 .. option:: log_store_compressed=bool
4111 If set, fio will store the log files in a compressed format. They can be
4112 decompressed with fio, using the :option:`--inflate-log` command line
4113 parameter. The files will be stored with a :file:`.fz` suffix.
4115 .. option:: log_unix_epoch=bool
4117 If set, fio will log Unix timestamps to the log files produced by enabling
4118 write_type_log for each log type, instead of the default zero-based
4121 .. option:: log_alternate_epoch=bool
4123 If set, fio will log timestamps based on the epoch used by the clock specified
4124 in the log_alternate_epoch_clock_id option, to the log files produced by
4125 enabling write_type_log for each log type, instead of the default zero-based
4128 .. option:: log_alternate_epoch_clock_id=int
4130 Specifies the clock_id to be used by clock_gettime to obtain the alternate epoch
4131 if either log_unix_epoch or log_alternate_epoch are true. Otherwise has no
4132 effect. Default value is 0, or CLOCK_REALTIME.
4134 .. option:: block_error_percentiles=bool
4136 If set, record errors in trim block-sized units from writes and trims and
4137 output a histogram of how many trims it took to get to errors, and what kind
4138 of error was encountered.
4140 .. option:: bwavgtime=int
4142 Average the calculated bandwidth over the given time. Value is specified in
4143 milliseconds. If the job also does bandwidth logging through
4144 :option:`write_bw_log`, then the minimum of this option and
4145 :option:`log_avg_msec` will be used. Default: 500ms.
4147 .. option:: iopsavgtime=int
4149 Average the calculated IOPS over the given time. Value is specified in
4150 milliseconds. If the job also does IOPS logging through
4151 :option:`write_iops_log`, then the minimum of this option and
4152 :option:`log_avg_msec` will be used. Default: 500ms.
4154 .. option:: disk_util=bool
4156 Generate disk utilization statistics, if the platform supports it.
4159 .. option:: disable_lat=bool
4161 Disable measurements of total latency numbers. Useful only for cutting back
4162 the number of calls to :manpage:`gettimeofday(2)`, as that does impact
4163 performance at really high IOPS rates. Note that to really get rid of a
4164 large amount of these calls, this option must be used with
4165 :option:`disable_slat` and :option:`disable_bw_measurement` as well.
4167 .. option:: disable_clat=bool
4169 Disable measurements of completion latency numbers. See
4170 :option:`disable_lat`.
4172 .. option:: disable_slat=bool
4174 Disable measurements of submission latency numbers. See
4175 :option:`disable_lat`.
4177 .. option:: disable_bw_measurement=bool, disable_bw=bool
4179 Disable measurements of throughput/bandwidth numbers. See
4180 :option:`disable_lat`.
4182 .. option:: slat_percentiles=bool
4184 Report submission latency percentiles. Submission latency is not recorded
4185 for synchronous ioengines.
4187 .. option:: clat_percentiles=bool
4189 Report completion latency percentiles.
4191 .. option:: lat_percentiles=bool
4193 Report total latency percentiles. Total latency is the sum of submission
4194 latency and completion latency.
4196 .. option:: percentile_list=float_list
4198 Overwrite the default list of percentiles for latencies and the block error
4199 histogram. Each number is a floating point number in the range (0,100], and
4200 the maximum length of the list is 20. Use ``:`` to separate the numbers. For
4201 example, ``--percentile_list=99.5:99.9`` will cause fio to report the
4202 latency durations below which 99.5% and 99.9% of the observed latencies fell,
4205 .. option:: significant_figures=int
4207 If using :option:`--output-format` of `normal`, set the significant
4208 figures to this value. Higher values will yield more precise IOPS and
4209 throughput units, while lower values will round. Requires a minimum
4210 value of 1 and a maximum value of 10. Defaults to 4.
4216 .. option:: exitall_on_error
4218 When one job finishes in error, terminate the rest. The default is to wait
4219 for each job to finish.
4221 .. option:: continue_on_error=str
4223 Normally fio will exit the job on the first observed failure. If this option
4224 is set, fio will continue the job when there is a 'non-fatal error' (EIO or
4225 EILSEQ) until the runtime is exceeded or the I/O size specified is
4226 completed. If this option is used, there are two more stats that are
4227 appended, the total error count and the first error. The error field given
4228 in the stats is the first error that was hit during the run.
4230 Note: a write error from the device may go unnoticed by fio when using
4231 buffered IO, as the write() (or similar) system call merely dirties the
4232 kernel pages, unless :option:`sync` or :option:`direct` is used. Device IO
4233 errors occur when the dirty data is actually written out to disk. If fully
4234 sync writes aren't desirable, :option:`fsync` or :option:`fdatasync` can be
4235 used as well. This is specific to writes, as reads are always synchronous.
4237 The allowed values are:
4240 Exit on any I/O or verify errors.
4243 Continue on read errors, exit on all others.
4246 Continue on write errors, exit on all others.
4249 Continue on any I/O error, exit on all others.
4252 Continue on verify errors, exit on all others.
4255 Continue on all errors.
4258 Backward-compatible alias for 'none'.
4261 Backward-compatible alias for 'all'.
4263 .. option:: ignore_error=str
4265 Sometimes you want to ignore some errors during test in that case you can
4266 specify error list for each error type, instead of only being able to
4267 ignore the default 'non-fatal error' using :option:`continue_on_error`.
4268 ``ignore_error=READ_ERR_LIST,WRITE_ERR_LIST,VERIFY_ERR_LIST`` errors for
4269 given error type is separated with ':'. Error may be symbol ('ENOSPC',
4270 'ENOMEM') or integer. Example::
4272 ignore_error=EAGAIN,ENOSPC:122
4274 This option will ignore EAGAIN from READ, and ENOSPC and 122(EDQUOT) from
4275 WRITE. This option works by overriding :option:`continue_on_error` with
4276 the list of errors for each error type if any.
4278 .. option:: error_dump=bool
4280 If set dump every error even if it is non fatal, true by default. If
4281 disabled only fatal error will be dumped.
4283 Running predefined workloads
4284 ----------------------------
4286 Fio includes predefined profiles that mimic the I/O workloads generated by
4289 .. option:: profile=str
4291 The predefined workload to run. Current profiles are:
4294 Threaded I/O bench (tiotest/tiobench) like workload.
4297 Aerospike Certification Tool (ACT) like workload.
4299 To view a profile's additional options use :option:`--cmdhelp` after specifying
4300 the profile. For example::
4302 $ fio --profile=act --cmdhelp
4307 .. option:: device-names=str
4312 .. option:: load=int
4315 ACT load multiplier. Default: 1.
4317 .. option:: test-duration=time
4320 How long the entire test takes to run. When the unit is omitted, the value
4321 is given in seconds. Default: 24h.
4323 .. option:: threads-per-queue=int
4326 Number of read I/O threads per device. Default: 8.
4328 .. option:: read-req-num-512-blocks=int
4331 Number of 512B blocks to read at the time. Default: 3.
4333 .. option:: large-block-op-kbytes=int
4336 Size of large block ops in KiB (writes). Default: 131072.
4341 Set to run ACT prep phase.
4343 Tiobench profile options
4344 ~~~~~~~~~~~~~~~~~~~~~~~~
4346 .. option:: size=str
4351 .. option:: block=int
4354 Block size in bytes. Default: 4096.
4356 .. option:: numruns=int
4366 .. option:: threads=int
4371 Interpreting the output
4372 -----------------------
4375 Example output was based on the following:
4376 TZ=UTC fio --iodepth=8 --ioengine=null --size=100M --time_based \
4377 --rate=1256k --bs=14K --name=quick --runtime=1s --name=mixed \
4378 --runtime=2m --rw=rw
4380 Fio spits out a lot of output. While running, fio will display the status of the
4381 jobs created. An example of that would be::
4383 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]
4385 The characters inside the first set of square brackets denote the current status of
4386 each thread. The first character is the first job defined in the job file, and so
4387 forth. The possible values (in typical life cycle order) are:
4389 +------+-----+-----------------------------------------------------------+
4391 +======+=====+===========================================================+
4392 | P | | Thread setup, but not started. |
4393 +------+-----+-----------------------------------------------------------+
4394 | C | | Thread created. |
4395 +------+-----+-----------------------------------------------------------+
4396 | I | | Thread initialized, waiting or generating necessary data. |
4397 +------+-----+-----------------------------------------------------------+
4398 | | p | Thread running pre-reading file(s). |
4399 +------+-----+-----------------------------------------------------------+
4400 | | / | Thread is in ramp period. |
4401 +------+-----+-----------------------------------------------------------+
4402 | | R | Running, doing sequential reads. |
4403 +------+-----+-----------------------------------------------------------+
4404 | | r | Running, doing random reads. |
4405 +------+-----+-----------------------------------------------------------+
4406 | | W | Running, doing sequential writes. |
4407 +------+-----+-----------------------------------------------------------+
4408 | | w | Running, doing random writes. |
4409 +------+-----+-----------------------------------------------------------+
4410 | | M | Running, doing mixed sequential reads/writes. |
4411 +------+-----+-----------------------------------------------------------+
4412 | | m | Running, doing mixed random reads/writes. |
4413 +------+-----+-----------------------------------------------------------+
4414 | | D | Running, doing sequential trims. |
4415 +------+-----+-----------------------------------------------------------+
4416 | | d | Running, doing random trims. |
4417 +------+-----+-----------------------------------------------------------+
4418 | | F | Running, currently waiting for :manpage:`fsync(2)`. |
4419 +------+-----+-----------------------------------------------------------+
4420 | | V | Running, doing verification of written data. |
4421 +------+-----+-----------------------------------------------------------+
4422 | f | | Thread finishing. |
4423 +------+-----+-----------------------------------------------------------+
4424 | E | | Thread exited, not reaped by main thread yet. |
4425 +------+-----+-----------------------------------------------------------+
4426 | _ | | Thread reaped. |
4427 +------+-----+-----------------------------------------------------------+
4428 | X | | Thread reaped, exited with an error. |
4429 +------+-----+-----------------------------------------------------------+
4430 | K | | Thread reaped, exited due to signal. |
4431 +------+-----+-----------------------------------------------------------+
4434 Example output was based on the following:
4435 TZ=UTC fio --iodepth=8 --ioengine=null --size=100M --runtime=58m \
4436 --time_based --rate=2512k --bs=256K --numjobs=10 \
4437 --name=readers --rw=read --name=writers --rw=write
4439 Fio will condense the thread string as not to take up more space on the command
4440 line than needed. For instance, if you have 10 readers and 10 writers running,
4441 the output would look like this::
4443 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]
4445 Note that the status string is displayed in order, so it's possible to tell which of
4446 the jobs are currently doing what. In the example above this means that jobs 1--10
4447 are readers and 11--20 are writers.
4449 The other values are fairly self explanatory -- number of threads currently
4450 running and doing I/O, the number of currently open files (f=), the estimated
4451 completion percentage, the rate of I/O since last check (read speed listed first,
4452 then write speed and optionally trim speed) in terms of bandwidth and IOPS,
4453 and time to completion for the current running group. It's impossible to estimate
4454 runtime of the following groups (if any).
4457 Example output was based on the following:
4458 TZ=UTC fio --iodepth=16 --ioengine=posixaio --filename=/tmp/fiofile \
4459 --direct=1 --size=100M --time_based --runtime=50s --rate_iops=89 \
4460 --bs=7K --name=Client1 --rw=write
4462 When fio is done (or interrupted by :kbd:`Ctrl-C`), it will show the data for
4463 each thread, group of threads, and disks in that order. For each overall thread (or
4464 group) the output looks like::
4466 Client1: (groupid=0, jobs=1): err= 0: pid=16109: Sat Jun 24 12:07:54 2017
4467 write: IOPS=88, BW=623KiB/s (638kB/s)(30.4MiB/50032msec)
4468 slat (nsec): min=500, max=145500, avg=8318.00, stdev=4781.50
4469 clat (usec): min=170, max=78367, avg=4019.02, stdev=8293.31
4470 lat (usec): min=174, max=78375, avg=4027.34, stdev=8291.79
4471 clat percentiles (usec):
4472 | 1.00th=[ 302], 5.00th=[ 326], 10.00th=[ 343], 20.00th=[ 363],
4473 | 30.00th=[ 392], 40.00th=[ 404], 50.00th=[ 416], 60.00th=[ 445],
4474 | 70.00th=[ 816], 80.00th=[ 6718], 90.00th=[12911], 95.00th=[21627],
4475 | 99.00th=[43779], 99.50th=[51643], 99.90th=[68682], 99.95th=[72877],
4477 bw ( KiB/s): min= 532, max= 686, per=0.10%, avg=622.87, stdev=24.82, samples= 100
4478 iops : min= 76, max= 98, avg=88.98, stdev= 3.54, samples= 100
4479 lat (usec) : 250=0.04%, 500=64.11%, 750=4.81%, 1000=2.79%
4480 lat (msec) : 2=4.16%, 4=1.84%, 10=4.90%, 20=11.33%, 50=5.37%
4481 lat (msec) : 100=0.65%
4482 cpu : usr=0.27%, sys=0.18%, ctx=12072, majf=0, minf=21
4483 IO depths : 1=85.0%, 2=13.1%, 4=1.8%, 8=0.1%, 16=0.0%, 32=0.0%, >=64=0.0%
4484 submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
4485 complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
4486 issued rwt: total=0,4450,0, short=0,0,0, dropped=0,0,0
4487 latency : target=0, window=0, percentile=100.00%, depth=8
4489 The job name (or first job's name when using :option:`group_reporting`) is printed,
4490 along with the group id, count of jobs being aggregated, last error id seen (which
4491 is 0 when there are no errors), pid/tid of that thread and the time the job/group
4492 completed. Below are the I/O statistics for each data direction performed (showing
4493 writes in the example above). In the order listed, they denote:
4496 The string before the colon shows the I/O direction the statistics
4497 are for. **IOPS** is the average I/Os performed per second. **BW**
4498 is the average bandwidth rate shown as: value in power of 2 format
4499 (value in power of 10 format). The last two values show: (**total
4500 I/O performed** in power of 2 format / **runtime** of that thread).
4503 Submission latency (**min** being the minimum, **max** being the
4504 maximum, **avg** being the average, **stdev** being the standard
4505 deviation). This is the time from when fio initialized the I/O
4506 to submission. For synchronous ioengines this includes the time
4507 up until just before the ioengine's queue function is called.
4508 For asynchronous ioengines this includes the time up through the
4509 completion of the ioengine's queue function (and commit function
4510 if it is defined). For sync I/O this row is not displayed as the
4511 slat is negligible. This value can be in nanoseconds,
4512 microseconds or milliseconds --- fio will choose the most
4513 appropriate base and print that (in the example above
4514 nanoseconds was the best scale). Note: in :option:`--minimal`
4515 mode latencies are always expressed in microseconds.
4518 Completion latency. Same names as slat, this denotes the time from
4519 submission to completion of the I/O pieces. For sync I/O, this
4520 represents the time from when the I/O was submitted to the
4521 operating system to when it was completed. For asynchronous
4522 ioengines this is the time from when the ioengine's queue (and
4523 commit if available) functions were completed to when the I/O's
4524 completion was reaped by fio.
4527 Total latency. Same names as slat and clat, this denotes the time from
4528 when fio created the I/O unit to completion of the I/O operation.
4529 It is the sum of submission and completion latency.
4532 Bandwidth statistics based on measurements from discrete
4533 intervals. Fio continuously monitors bytes transferred and I/O
4534 operations completed. By default fio calculates bandwidth in
4535 each half-second interval (see :option:`bwavgtime`) and reports
4536 descriptive statistics for the measurements here. Same names as
4537 the xlat stats, but also includes the number of samples taken
4538 (**samples**) and an approximate percentage of total aggregate
4539 bandwidth this thread received in its group (**per**). This
4540 last value is only really useful if the threads in this group
4541 are on the same disk, since they are then competing for disk
4545 IOPS statistics based on measurements from discrete intervals.
4546 For details see the description for bw above. See
4547 :option:`iopsavgtime` to control the duration of the intervals.
4548 Same values reported here as for bw except for percentage.
4550 **lat (nsec/usec/msec)**
4551 The distribution of I/O completion latencies. This is the time from when
4552 I/O leaves fio and when it gets completed. Unlike the separate
4553 read/write/trim sections above, the data here and in the remaining
4554 sections apply to all I/Os for the reporting group. 250=0.04% means that
4555 0.04% of the I/Os completed in under 250us. 500=64.11% means that 64.11%
4556 of the I/Os required 250 to 499us for completion.
4559 CPU usage. User and system time, along with the number of context
4560 switches this thread went through, usage of system and user time, and
4561 finally the number of major and minor page faults. The CPU utilization
4562 numbers are averages for the jobs in that reporting group, while the
4563 context and fault counters are summed.
4566 The distribution of I/O depths over the job lifetime. The numbers are
4567 divided into powers of 2 and each entry covers depths from that value
4568 up to those that are lower than the next entry -- e.g., 16= covers
4569 depths from 16 to 31. Note that the range covered by a depth
4570 distribution entry can be different to the range covered by the
4571 equivalent submit/complete distribution entry.
4574 How many pieces of I/O were submitting in a single submit call. Each
4575 entry denotes that amount and below, until the previous entry -- e.g.,
4576 16=100% means that we submitted anywhere between 9 to 16 I/Os per submit
4577 call. Note that the range covered by a submit distribution entry can
4578 be different to the range covered by the equivalent depth distribution
4582 Like the above submit number, but for completions instead.
4585 The number of read/write/trim requests issued, and how many of them were
4589 These values are for :option:`latency_target` and related options. When
4590 these options are engaged, this section describes the I/O depth required
4591 to meet the specified latency target.
4594 Example output was based on the following:
4595 TZ=UTC fio --ioengine=null --iodepth=2 --size=100M --numjobs=2 \
4596 --rate_process=poisson --io_limit=32M --name=read --bs=128k \
4597 --rate=11M --name=write --rw=write --bs=2k --rate=700k
4599 After each client has been listed, the group statistics are printed. They
4600 will look like this::
4602 Run status group 0 (all jobs):
4603 READ: bw=20.9MiB/s (21.9MB/s), 10.4MiB/s-10.8MiB/s (10.9MB/s-11.3MB/s), io=64.0MiB (67.1MB), run=2973-3069msec
4604 WRITE: bw=1231KiB/s (1261kB/s), 616KiB/s-621KiB/s (630kB/s-636kB/s), io=64.0MiB (67.1MB), run=52747-53223msec
4606 For each data direction it prints:
4609 Aggregate bandwidth of threads in this group followed by the
4610 minimum and maximum bandwidth of all the threads in this group.
4611 Values outside of brackets are power-of-2 format and those
4612 within are the equivalent value in a power-of-10 format.
4614 Aggregate I/O performed of all threads in this group. The
4615 format is the same as bw.
4617 The smallest and longest runtimes of the threads in this group.
4619 And finally, the disk statistics are printed. This is Linux specific. They will look like this::
4621 Disk stats (read/write):
4622 sda: ios=16398/16511, sectors=32321/65472, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00%
4624 Each value is printed for both reads and writes, with reads first. The
4628 Number of I/Os performed by all groups.
4630 Amount of data transferred in units of 512 bytes for all groups.
4632 Number of merges performed by the I/O scheduler.
4634 Number of ticks we kept the disk busy.
4636 Total time spent in the disk queue.
4638 The disk utilization. A value of 100% means we kept the disk
4639 busy constantly, 50% would be a disk idling half of the time.
4641 It is also possible to get fio to dump the current output while it is running,
4642 without terminating the job. To do that, send fio the **USR1** signal. You can
4643 also get regularly timed dumps by using the :option:`--status-interval`
4644 parameter, or by creating a file in :file:`/tmp` named
4645 :file:`fio-dump-status`. If fio sees this file, it will unlink it and dump the
4646 current output status.
4652 For scripted usage where you typically want to generate tables or graphs of the
4653 results, fio can output the results in a semicolon separated format. The format
4654 is one long line of values, such as::
4656 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%
4657 A description of this job goes here.
4659 The job description (if provided) follows on a second line for terse v2.
4660 It appears on the same line for other terse versions.
4662 To enable terse output, use the :option:`--minimal` or
4663 :option:`--output-format`\=terse command line options. The
4664 first value is the version of the terse output format. If the output has to be
4665 changed for some reason, this number will be incremented by 1 to signify that
4668 Split up, the format is as follows (comments in brackets denote when a
4669 field was introduced or whether it's specific to some terse version):
4673 terse version, fio version [v3], jobname, groupid, error
4677 Total IO (KiB), bandwidth (KiB/sec), IOPS, runtime (msec)
4678 Submission latency: min, max, mean, stdev (usec)
4679 Completion latency: min, max, mean, stdev (usec)
4680 Completion latency percentiles: 20 fields (see below)
4681 Total latency: min, max, mean, stdev (usec)
4682 Bw (KiB/s): min, max, aggregate percentage of total, mean, stdev, number of samples [v5]
4683 IOPS [v5]: min, max, mean, stdev, number of samples
4689 Total IO (KiB), bandwidth (KiB/sec), IOPS, runtime (msec)
4690 Submission latency: min, max, mean, stdev (usec)
4691 Completion latency: min, max, mean, stdev (usec)
4692 Completion latency percentiles: 20 fields (see below)
4693 Total latency: min, max, mean, stdev (usec)
4694 Bw (KiB/s): min, max, aggregate percentage of total, mean, stdev, number of samples [v5]
4695 IOPS [v5]: min, max, mean, stdev, number of samples
4697 TRIM status [all but version 3]:
4699 Fields are similar to READ/WRITE status.
4703 user, system, context switches, major faults, minor faults
4707 <=1, 2, 4, 8, 16, 32, >=64
4709 I/O latencies microseconds::
4711 <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000
4713 I/O latencies milliseconds::
4715 <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, 2000, >=2000
4717 Disk utilization [v3]::
4719 disk name, read ios, write ios, read merges, write merges, read ticks, write ticks,
4720 time spent in queue, disk utilization percentage
4722 Additional Info (dependent on continue_on_error, default off)::
4724 total # errors, first error code
4726 Additional Info (dependent on description being set)::
4730 Completion latency percentiles can be a grouping of up to 20 sets, so for the
4731 terse output fio writes all of them. Each field will look like this::
4735 which is the Xth percentile, and the `usec` latency associated with it.
4737 For `Disk utilization`, all disks used by fio are shown. So for each disk there
4738 will be a disk utilization section.
4740 Below is a single line containing short names for each of the fields in the
4741 minimal output v3, separated by semicolons::
4743 terse_version_3;fio_version;jobname;groupid;error;read_kb;read_bandwidth_kb;read_iops;read_runtime_ms;read_slat_min_us;read_slat_max_us;read_slat_mean_us;read_slat_dev_us;read_clat_min_us;read_clat_max_us;read_clat_mean_us;read_clat_dev_us;read_clat_pct01;read_clat_pct02;read_clat_pct03;read_clat_pct04;read_clat_pct05;read_clat_pct06;read_clat_pct07;read_clat_pct08;read_clat_pct09;read_clat_pct10;read_clat_pct11;read_clat_pct12;read_clat_pct13;read_clat_pct14;read_clat_pct15;read_clat_pct16;read_clat_pct17;read_clat_pct18;read_clat_pct19;read_clat_pct20;read_tlat_min_us;read_lat_max_us;read_lat_mean_us;read_lat_dev_us;read_bw_min_kb;read_bw_max_kb;read_bw_agg_pct;read_bw_mean_kb;read_bw_dev_kb;write_kb;write_bandwidth_kb;write_iops;write_runtime_ms;write_slat_min_us;write_slat_max_us;write_slat_mean_us;write_slat_dev_us;write_clat_min_us;write_clat_max_us;write_clat_mean_us;write_clat_dev_us;write_clat_pct01;write_clat_pct02;write_clat_pct03;write_clat_pct04;write_clat_pct05;write_clat_pct06;write_clat_pct07;write_clat_pct08;write_clat_pct09;write_clat_pct10;write_clat_pct11;write_clat_pct12;write_clat_pct13;write_clat_pct14;write_clat_pct15;write_clat_pct16;write_clat_pct17;write_clat_pct18;write_clat_pct19;write_clat_pct20;write_tlat_min_us;write_lat_max_us;write_lat_mean_us;write_lat_dev_us;write_bw_min_kb;write_bw_max_kb;write_bw_agg_pct;write_bw_mean_kb;write_bw_dev_kb;cpu_user;cpu_sys;cpu_csw;cpu_mjf;cpu_minf;iodepth_1;iodepth_2;iodepth_4;iodepth_8;iodepth_16;iodepth_32;iodepth_64;lat_2us;lat_4us;lat_10us;lat_20us;lat_50us;lat_100us;lat_250us;lat_500us;lat_750us;lat_1000us;lat_2ms;lat_4ms;lat_10ms;lat_20ms;lat_50ms;lat_100ms;lat_250ms;lat_500ms;lat_750ms;lat_1000ms;lat_2000ms;lat_over_2000ms;disk_name;disk_read_iops;disk_write_iops;disk_read_merges;disk_write_merges;disk_read_ticks;write_ticks;disk_queue_time;disk_util
4745 In client/server mode terse output differs from what appears when jobs are run
4746 locally. Disk utilization data is omitted from the standard terse output and
4747 for v3 and later appears on its own separate line at the end of each terse
4754 The `json` output format is intended to be both human readable and convenient
4755 for automated parsing. For the most part its sections mirror those of the
4756 `normal` output. The `runtime` value is reported in msec and the `bw` value is
4757 reported in 1024 bytes per second units.
4763 The `json+` output format is identical to the `json` output format except that it
4764 adds a full dump of the completion latency bins. Each `bins` object contains a
4765 set of (key, value) pairs where keys are latency durations and values count how
4766 many I/Os had completion latencies of the corresponding duration. For example,
4769 "bins" : { "87552" : 1, "89600" : 1, "94720" : 1, "96768" : 1, "97792" : 1, "99840" : 1, "100864" : 2, "103936" : 6, "104960" : 534, "105984" : 5995, "107008" : 7529, ... }
4771 This data indicates that one I/O required 87,552ns to complete, two I/Os required
4772 100,864ns to complete, and 7529 I/Os required 107,008ns to complete.
4774 Also included with fio is a Python script `fio_jsonplus_clat2csv` that takes
4775 json+ output and generates CSV-formatted latency data suitable for plotting.
4777 The latency durations actually represent the midpoints of latency intervals.
4778 For details refer to :file:`stat.h`.
4784 There are two trace file format that you can encounter. The older (v1) format is
4785 unsupported since version 1.20-rc3 (March 2008). It will still be described
4786 below in case that you get an old trace and want to understand it.
4788 In any case the trace is a simple text file with a single action per line.
4791 Trace file format v1
4792 ~~~~~~~~~~~~~~~~~~~~
4794 Each line represents a single I/O action in the following format::
4798 where `rw=0/1` for read/write, and the `offset` and `length` entries being in bytes.
4800 This format is not supported in fio versions >= 1.20-rc3.
4803 Trace file format v2
4804 ~~~~~~~~~~~~~~~~~~~~
4806 The second version of the trace file format was added in fio version 1.17. It
4807 allows one to access more than one file per trace and has a bigger set of possible
4810 The first line of the trace file has to be::
4814 Following this can be lines in two different formats, which are described below.
4816 The file management format::
4820 The `filename` is given as an absolute path. The `action` can be one of these:
4823 Add the given `filename` to the trace.
4825 Open the file with the given `filename`. The `filename` has to have
4826 been added with the **add** action before.
4828 Close the file with the given `filename`. The file has to have been
4832 The file I/O action format::
4834 filename action offset length
4836 The `filename` is given as an absolute path, and has to have been added and
4837 opened before it can be used with this format. The `offset` and `length` are
4838 given in bytes. The `action` can be one of these:
4841 Wait for `offset` microseconds. Everything below 100 is discarded.
4842 The time is relative to the previous `wait` statement. Note that
4843 action `wait` is not allowed as of version 3, as the same behavior
4844 can be achieved using timestamps.
4846 Read `length` bytes beginning from `offset`.
4848 Write `length` bytes beginning from `offset`.
4850 :manpage:`fsync(2)` the file.
4852 :manpage:`fdatasync(2)` the file.
4854 Trim the given file from the given `offset` for `length` bytes.
4857 Trace file format v3
4858 ~~~~~~~~~~~~~~~~~~~~
4860 The third version of the trace file format was added in fio version 3.31. It
4861 forces each action to have a timestamp associated with it.
4863 The first line of the trace file has to be::
4867 Following this can be lines in two different formats, which are described below.
4869 The file management format::
4871 timestamp filename action
4873 The file I/O action format::
4875 timestamp filename action offset length
4877 The `timestamp` is relative to the beginning of the run (ie starts at 0). The
4878 `filename`, `action`, `offset` and `length` are identical to version 2, except
4879 that version 3 does not allow the `wait` action.
4882 I/O Replay - Merging Traces
4883 ---------------------------
4885 Colocation is a common practice used to get the most out of a machine.
4886 Knowing which workloads play nicely with each other and which ones don't is
4887 a much harder task. While fio can replay workloads concurrently via multiple
4888 jobs, it leaves some variability up to the scheduler making results harder to
4889 reproduce. Merging is a way to make the order of events consistent.
4891 Merging is integrated into I/O replay and done when a
4892 :option:`merge_blktrace_file` is specified. The list of files passed to
4893 :option:`read_iolog` go through the merge process and output a single file
4894 stored to the specified file. The output file is passed on as if it were the
4895 only file passed to :option:`read_iolog`. An example would look like::
4897 $ fio --read_iolog="<file1>:<file2>" --merge_blktrace_file="<output_file>"
4899 Creating only the merged file can be done by passing the command line argument
4900 :option:`--merge-blktrace-only`.
4902 Scaling traces can be done to see the relative impact of any particular trace
4903 being slowed down or sped up. :option:`merge_blktrace_scalars` takes in a colon
4904 separated list of percentage scalars. It is index paired with the files passed
4905 to :option:`read_iolog`.
4907 With scaling, it may be desirable to match the running time of all traces.
4908 This can be done with :option:`merge_blktrace_iters`. It is index paired with
4909 :option:`read_iolog` just like :option:`merge_blktrace_scalars`.
4911 In an example, given two traces, A and B, each 60s long. If we want to see
4912 the impact of trace A issuing IOs twice as fast and repeat trace A over the
4913 runtime of trace B, the following can be done::
4915 $ fio --read_iolog="<trace_a>:"<trace_b>" --merge_blktrace_file"<output_file>" --merge_blktrace_scalars="50:100" --merge_blktrace_iters="2:1"
4917 This runs trace A at 2x the speed twice for approximately the same runtime as
4918 a single run of trace B.
4921 CPU idleness profiling
4922 ----------------------
4924 In some cases, we want to understand CPU overhead in a test. For example, we
4925 test patches for the specific goodness of whether they reduce CPU usage.
4926 Fio implements a balloon approach to create a thread per CPU that runs at idle
4927 priority, meaning that it only runs when nobody else needs the cpu.
4928 By measuring the amount of work completed by the thread, idleness of each CPU
4929 can be derived accordingly.
4931 An unit work is defined as touching a full page of unsigned characters. Mean and
4932 standard deviation of time to complete an unit work is reported in "unit work"
4933 section. Options can be chosen to report detailed percpu idleness or overall
4934 system idleness by aggregating percpu stats.
4937 Verification and triggers
4938 -------------------------
4940 Fio is usually run in one of two ways, when data verification is done. The first
4941 is a normal write job of some sort with verify enabled. When the write phase has
4942 completed, fio switches to reads and verifies everything it wrote. The second
4943 model is running just the write phase, and then later on running the same job
4944 (but with reads instead of writes) to repeat the same I/O patterns and verify
4945 the contents. Both of these methods depend on the write phase being completed,
4946 as fio otherwise has no idea how much data was written.
4948 With verification triggers, fio supports dumping the current write state to
4949 local files. Then a subsequent read verify workload can load this state and know
4950 exactly where to stop. This is useful for testing cases where power is cut to a
4951 server in a managed fashion, for instance.
4953 A verification trigger consists of two things:
4955 1) Storing the write state of each job.
4956 2) Executing a trigger command.
4958 The write state is relatively small, on the order of hundreds of bytes to single
4959 kilobytes. It contains information on the number of completions done, the last X
4962 A trigger is invoked either through creation ('touch') of a specified file in
4963 the system, or through a timeout setting. If fio is run with
4964 :option:`--trigger-file`\= :file:`/tmp/trigger-file`, then it will continually
4965 check for the existence of :file:`/tmp/trigger-file`. When it sees this file, it
4966 will fire off the trigger (thus saving state, and executing the trigger
4969 For client/server runs, there's both a local and remote trigger. If fio is
4970 running as a server backend, it will send the job states back to the client for
4971 safe storage, then execute the remote trigger, if specified. If a local trigger
4972 is specified, the server will still send back the write state, but the client
4973 will then execute the trigger.
4975 Verification trigger example
4976 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
4978 Let's say we want to run a powercut test on the remote Linux machine 'server'.
4979 Our write workload is in :file:`write-test.fio`. We want to cut power to 'server' at
4980 some point during the run, and we'll run this test from the safety or our local
4981 machine, 'localbox'. On the server, we'll start the fio backend normally::
4983 server# fio --server
4985 and on the client, we'll fire off the workload::
4987 localbox$ fio --client=server --trigger-file=/tmp/my-trigger --trigger-remote="bash -c \"echo b > /proc/sysrq-triger\""
4989 We set :file:`/tmp/my-trigger` as the trigger file, and we tell fio to execute::
4991 echo b > /proc/sysrq-trigger
4993 on the server once it has received the trigger and sent us the write state. This
4994 will work, but it's not **really** cutting power to the server, it's merely
4995 abruptly rebooting it. If we have a remote way of cutting power to the server
4996 through IPMI or similar, we could do that through a local trigger command
4997 instead. Let's assume we have a script that does IPMI reboot of a given hostname,
4998 ipmi-reboot. On localbox, we could then have run fio with a local trigger
5001 localbox$ fio --client=server --trigger-file=/tmp/my-trigger --trigger="ipmi-reboot server"
5003 For this case, fio would wait for the server to send us the write state, then
5004 execute ``ipmi-reboot server`` when that happened.
5006 Loading verify state
5007 ~~~~~~~~~~~~~~~~~~~~
5009 To load stored write state, a read verification job file must contain the
5010 :option:`verify_state_load` option. If that is set, fio will load the previously
5011 stored state. For a local fio run this is done by loading the files directly,
5012 and on a client/server run, the server backend will ask the client to send the
5013 files over and load them from there.
5019 Fio supports a variety of log file formats, for logging latencies, bandwidth,
5020 and IOPS. The logs share a common format, which looks like this:
5022 *time* (`msec`), *value*, *data direction*, *block size* (`bytes`),
5023 *offset* (`bytes`), *command priority*
5025 *Time* for the log entry is always in milliseconds. The *value* logged depends
5026 on the type of log, it will be one of the following:
5029 Value is latency in nsecs
5035 *Data direction* is one of the following:
5044 The entry's *block size* is always in bytes. The *offset* is the position in bytes
5045 from the start of the file for that particular I/O. The logging of the offset can be
5046 toggled with :option:`log_offset`.
5048 *Command priority* is 0 for normal priority and 1 for high priority. This is controlled
5049 by the ioengine specific :option:`cmdprio_percentage`.
5051 Fio defaults to logging every individual I/O but when windowed logging is set
5052 through :option:`log_avg_msec`, either the average (by default) or the maximum
5053 (:option:`log_max_value` is set) *value* seen over the specified period of time
5054 is recorded. Each *data direction* seen within the window period will aggregate
5055 its values in a separate row. Further, when using windowed logging the *block
5056 size* and *offset* entries will always contain 0.
5062 Normally fio is invoked as a stand-alone application on the machine where the
5063 I/O workload should be generated. However, the backend and frontend of fio can
5064 be run separately i.e., the fio server can generate an I/O workload on the "Device
5065 Under Test" while being controlled by a client on another machine.
5067 Start the server on the machine which has access to the storage DUT::
5071 where `args` defines what fio listens to. The arguments are of the form
5072 ``type,hostname`` or ``IP,port``. *type* is either ``ip`` (or ip4) for TCP/IP
5073 v4, ``ip6`` for TCP/IP v6, or ``sock`` for a local unix domain socket.
5074 *hostname* is either a hostname or IP address, and *port* is the port to listen
5075 to (only valid for TCP/IP, not a local socket). Some examples:
5079 Start a fio server, listening on all interfaces on the default port (8765).
5081 2) ``fio --server=ip:hostname,4444``
5083 Start a fio server, listening on IP belonging to hostname and on port 4444.
5085 3) ``fio --server=ip6:::1,4444``
5087 Start a fio server, listening on IPv6 localhost ::1 and on port 4444.
5089 4) ``fio --server=,4444``
5091 Start a fio server, listening on all interfaces on port 4444.
5093 5) ``fio --server=1.2.3.4``
5095 Start a fio server, listening on IP 1.2.3.4 on the default port.
5097 6) ``fio --server=sock:/tmp/fio.sock``
5099 Start a fio server, listening on the local socket :file:`/tmp/fio.sock`.
5101 Once a server is running, a "client" can connect to the fio server with::
5103 fio <local-args> --client=<server> <remote-args> <job file(s)>
5105 where `local-args` are arguments for the client where it is running, `server`
5106 is the connect string, and `remote-args` and `job file(s)` are sent to the
5107 server. The `server` string follows the same format as it does on the server
5108 side, to allow IP/hostname/socket and port strings.
5110 Fio can connect to multiple servers this way::
5112 fio --client=<server1> <job file(s)> --client=<server2> <job file(s)>
5114 If the job file is located on the fio server, then you can tell the server to
5115 load a local file as well. This is done by using :option:`--remote-config` ::
5117 fio --client=server --remote-config /path/to/file.fio
5119 Then fio will open this local (to the server) job file instead of being passed
5120 one from the client.
5122 If you have many servers (example: 100 VMs/containers), you can input a pathname
5123 of a file containing host IPs/names as the parameter value for the
5124 :option:`--client` option. For example, here is an example :file:`host.list`
5125 file containing 2 hostnames::
5127 host1.your.dns.domain
5128 host2.your.dns.domain
5130 The fio command would then be::
5132 fio --client=host.list <job file(s)>
5134 In this mode, you cannot input server-specific parameters or job files -- all
5135 servers receive the same job file.
5137 In order to let ``fio --client`` runs use a shared filesystem from multiple
5138 hosts, ``fio --client`` now prepends the IP address of the server to the
5139 filename. For example, if fio is using the directory :file:`/mnt/nfs/fio` and is
5140 writing filename :file:`fileio.tmp`, with a :option:`--client` `hostfile`
5141 containing two hostnames ``h1`` and ``h2`` with IP addresses 192.168.10.120 and
5142 192.168.10.121, then fio will create two files::
5144 /mnt/nfs/fio/192.168.10.120.fileio.tmp
5145 /mnt/nfs/fio/192.168.10.121.fileio.tmp
5147 Terse output in client/server mode will differ slightly from what is produced
5148 when fio is run in stand-alone mode. See the terse output section for details.