doc: add cpus_allowed reference to log_compression_cpus
[fio.git] / HOWTO
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1How fio works
2-------------
3
4The first step in getting fio to simulate a desired I/O workload, is writing a
5job file describing that specific setup. A job file may contain any number of
6threads and/or files -- the typical contents of the job file is a *global*
7section defining shared parameters, and one or more job sections describing the
8jobs involved. When run, fio parses this file and sets everything up as
9described. If we break down a job from top to bottom, it contains the following
10basic parameters:
11
12`I/O type`_
13
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?
18
19`Block size`_
20
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.
23
24`I/O size`_
25
26 How much data are we going to be reading/writing.
27
28`I/O engine`_
29
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
32 SG (SCSI generic sg).
33
34`I/O depth`_
35
36 If the I/O engine is async, how large a queuing depth do we want to
37 maintain?
38
39
40`Target file/device`_
41
42 How many files are we spreading the workload over.
43
44`Threads, processes and job synchronization`_
45
46 How many threads or processes should we spread this workload over.
47
48The above are the basic parameters defined for a workload, in addition there's a
49multitude of parameters that modify other aspects of how this job behaves.
50
51
52Command line options
53--------------------
54
55.. option:: --debug=type
56
f50fbdda 57 Enable verbose tracing `type` of various fio actions. May be ``all`` for all types
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58 or individual types separated by a comma (e.g. ``--debug=file,mem`` will
59 enable file and memory debugging). Currently, additional logging is
60 available for:
f80dba8d 61
b034c0dd 62 *process*
f80dba8d 63 Dump info related to processes.
b034c0dd 64 *file*
f80dba8d 65 Dump info related to file actions.
b034c0dd 66 *io*
f80dba8d 67 Dump info related to I/O queuing.
b034c0dd 68 *mem*
f80dba8d 69 Dump info related to memory allocations.
b034c0dd 70 *blktrace*
f80dba8d 71 Dump info related to blktrace setup.
b034c0dd 72 *verify*
f80dba8d 73 Dump info related to I/O verification.
b034c0dd 74 *all*
f80dba8d 75 Enable all debug options.
b034c0dd 76 *random*
f80dba8d 77 Dump info related to random offset generation.
b034c0dd 78 *parse*
f80dba8d 79 Dump info related to option matching and parsing.
b034c0dd 80 *diskutil*
f80dba8d 81 Dump info related to disk utilization updates.
b034c0dd 82 *job:x*
f80dba8d 83 Dump info only related to job number x.
b034c0dd 84 *mutex*
f80dba8d 85 Dump info only related to mutex up/down ops.
b034c0dd 86 *profile*
f80dba8d 87 Dump info related to profile extensions.
b034c0dd 88 *time*
f80dba8d 89 Dump info related to internal time keeping.
b034c0dd 90 *net*
f80dba8d 91 Dump info related to networking connections.
b034c0dd 92 *rate*
f80dba8d 93 Dump info related to I/O rate switching.
b034c0dd 94 *compress*
f80dba8d 95 Dump info related to log compress/decompress.
b034c0dd 96 *?* or *help*
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97 Show available debug options.
98
99.. option:: --parse-only
100
25cd4b95 101 Parse options only, don't start any I/O.
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102
103.. option:: --output=filename
104
105 Write output to file `filename`.
106
f50fbdda 107.. option:: --output-format=format
b8f7e412 108
f50fbdda 109 Set the reporting `format` to `normal`, `terse`, `json`, or `json+`. Multiple
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110 formats can be selected, separated by a comma. `terse` is a CSV based
111 format. `json+` is like `json`, except it adds a full dump of the latency
112 buckets.
113
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114.. option:: --bandwidth-log
115
116 Generate aggregate bandwidth logs.
117
118.. option:: --minimal
119
120 Print statistics in a terse, semicolon-delimited format.
121
122.. option:: --append-terse
123
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124 Print statistics in selected mode AND terse, semicolon-delimited format.
125 **Deprecated**, use :option:`--output-format` instead to select multiple
126 formats.
f80dba8d 127
f50fbdda 128.. option:: --terse-version=version
f80dba8d 129
f50fbdda 130 Set terse `version` output format (default 3, or 2 or 4 or 5).
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131
132.. option:: --version
133
b8f7e412 134 Print version information and exit.
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135
136.. option:: --help
137
113f0e7c 138 Print a summary of the command line options and exit.
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139
140.. option:: --cpuclock-test
141
142 Perform test and validation of internal CPU clock.
143
113f0e7c 144.. option:: --crctest=[test]
f80dba8d 145
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146 Test the speed of the built-in checksumming functions. If no argument is
147 given, all of them are tested. Alternatively, a comma separated list can
148 be passed, in which case the given ones are tested.
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149
150.. option:: --cmdhelp=command
151
152 Print help information for `command`. May be ``all`` for all commands.
153
154.. option:: --enghelp=[ioengine[,command]]
155
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156 List all commands defined by `ioengine`, or print help for `command`
157 defined by `ioengine`. If no `ioengine` is given, list all
b034c0dd 158 available ioengines.
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159
160.. option:: --showcmd=jobfile
161
b8f7e412 162 Convert `jobfile` to a set of command-line options.
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163
164.. option:: --readonly
165
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166 Turn on safety read-only checks, preventing writes. The ``--readonly``
167 option is an extra safety guard to prevent users from accidentally starting
168 a write workload when that is not desired. Fio will only write if
169 `rw=write/randwrite/rw/randrw` is given. This extra safety net can be used
170 as an extra precaution as ``--readonly`` will also enable a write check in
171 the I/O engine core to prevent writes due to unknown user space bug(s).
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172
173.. option:: --eta=when
174
b8f7e412 175 Specifies when real-time ETA estimate should be printed. `when` may be
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176 `always`, `never` or `auto`. `auto` is the default, it prints ETA
177 when requested if the output is a TTY. `always` disregards the output
178 type, and prints ETA when requested. `never` never prints ETA.
179
180.. option:: --eta-interval=time
181
182 By default, fio requests client ETA status roughly every second. With
183 this option, the interval is configurable. Fio imposes a minimum
184 allowed time to avoid flooding the console, less than 250 msec is
185 not supported.
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186
187.. option:: --eta-newline=time
188
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189 Force a new line for every `time` period passed. When the unit is omitted,
190 the value is interpreted in seconds.
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191
192.. option:: --status-interval=time
193
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194 Force a full status dump of cumulative (from job start) values at `time`
195 intervals. This option does *not* provide per-period measurements. So
196 values such as bandwidth are running averages. When the time unit is omitted,
197 `time` is interpreted in seconds.
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198
199.. option:: --section=name
200
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201 Only run specified section `name` in job file. Multiple sections can be specified.
202 The ``--section`` option allows one to combine related jobs into one file.
203 E.g. one job file could define light, moderate, and heavy sections. Tell
204 fio to run only the "heavy" section by giving ``--section=heavy``
205 command line option. One can also specify the "write" operations in one
206 section and "verify" operation in another section. The ``--section`` option
207 only applies to job sections. The reserved *global* section is always
208 parsed and used.
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209
210.. option:: --alloc-size=kb
211
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212 Set the internal smalloc pool size to `kb` in KiB. The
213 ``--alloc-size`` switch allows one to use a larger pool size for smalloc.
214 If running large jobs with randommap enabled, fio can run out of memory.
215 Smalloc is an internal allocator for shared structures from a fixed size
216 memory pool and can grow to 16 pools. The pool size defaults to 16MiB.
f80dba8d 217
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218 NOTE: While running :file:`.fio_smalloc.*` backing store files are visible
219 in :file:`/tmp`.
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220
221.. option:: --warnings-fatal
222
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223 All fio parser warnings are fatal, causing fio to exit with an
224 error.
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225
226.. option:: --max-jobs=nr
227
f50fbdda 228 Set the maximum number of threads/processes to support to `nr`.
818322cc 229 NOTE: On Linux, it may be necessary to increase the shared-memory
71aa48eb 230 limit (:file:`/proc/sys/kernel/shmmax`) if fio runs into errors while
818322cc 231 creating jobs.
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232
233.. option:: --server=args
234
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235 Start a backend server, with `args` specifying what to listen to.
236 See `Client/Server`_ section.
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237
238.. option:: --daemonize=pidfile
239
b034c0dd 240 Background a fio server, writing the pid to the given `pidfile` file.
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241
242.. option:: --client=hostname
243
f50fbdda 244 Instead of running the jobs locally, send and run them on the given `hostname`
71aa48eb 245 or set of `hostname`\s. See `Client/Server`_ section.
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246
247.. option:: --remote-config=file
248
f50fbdda 249 Tell fio server to load this local `file`.
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250
251.. option:: --idle-prof=option
252
b8f7e412 253 Report CPU idleness. `option` is one of the following:
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254
255 **calibrate**
256 Run unit work calibration only and exit.
257
258 **system**
259 Show aggregate system idleness and unit work.
260
261 **percpu**
262 As **system** but also show per CPU idleness.
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263
264.. option:: --inflate-log=log
265
f50fbdda 266 Inflate and output compressed `log`.
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267
268.. option:: --trigger-file=file
269
f50fbdda 270 Execute trigger command when `file` exists.
f80dba8d 271
f50fbdda 272.. option:: --trigger-timeout=time
f80dba8d 273
f50fbdda 274 Execute trigger at this `time`.
f80dba8d 275
f50fbdda 276.. option:: --trigger=command
f80dba8d 277
f50fbdda 278 Set this `command` as local trigger.
f80dba8d 279
f50fbdda 280.. option:: --trigger-remote=command
f80dba8d 281
f50fbdda 282 Set this `command` as remote trigger.
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283
284.. option:: --aux-path=path
285
f50fbdda 286 Use this `path` for fio state generated files.
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287
288Any parameters following the options will be assumed to be job files, unless
289they match a job file parameter. Multiple job files can be listed and each job
290file will be regarded as a separate group. Fio will :option:`stonewall`
291execution between each group.
292
293
294Job file format
295---------------
296
297As previously described, fio accepts one or more job files describing what it is
298supposed to do. The job file format is the classic ini file, where the names
c60ebc45 299enclosed in [] brackets define the job name. You are free to use any ASCII name
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300you want, except *global* which has special meaning. Following the job name is
301a sequence of zero or more parameters, one per line, that define the behavior of
302the job. If the first character in a line is a ';' or a '#', the entire line is
303discarded as a comment.
304
305A *global* section sets defaults for the jobs described in that file. A job may
306override a *global* section parameter, and a job file may even have several
307*global* sections if so desired. A job is only affected by a *global* section
308residing above it.
309
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310The :option:`--cmdhelp` option also lists all options. If used with a `command`
311argument, :option:`--cmdhelp` will detail the given `command`.
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312
313See the `examples/` directory for inspiration on how to write job files. Note
314the copyright and license requirements currently apply to `examples/` files.
315
316So let's look at a really simple job file that defines two processes, each
317randomly reading from a 128MiB file:
318
319.. code-block:: ini
320
321 ; -- start job file --
322 [global]
323 rw=randread
324 size=128m
325
326 [job1]
327
328 [job2]
329
330 ; -- end job file --
331
332As you can see, the job file sections themselves are empty as all the described
333parameters are shared. As no :option:`filename` option is given, fio makes up a
334`filename` for each of the jobs as it sees fit. On the command line, this job
335would look as follows::
336
337$ fio --name=global --rw=randread --size=128m --name=job1 --name=job2
338
339
340Let's look at an example that has a number of processes writing randomly to
341files:
342
343.. code-block:: ini
344
345 ; -- start job file --
346 [random-writers]
347 ioengine=libaio
348 iodepth=4
349 rw=randwrite
350 bs=32k
351 direct=0
352 size=64m
353 numjobs=4
354 ; -- end job file --
355
356Here we have no *global* section, as we only have one job defined anyway. We
357want to use async I/O here, with a depth of 4 for each file. We also increased
358the buffer size used to 32KiB and define numjobs to 4 to fork 4 identical
359jobs. The result is 4 processes each randomly writing to their own 64MiB
360file. Instead of using the above job file, you could have given the parameters
361on the command line. For this case, you would specify::
362
363$ fio --name=random-writers --ioengine=libaio --iodepth=4 --rw=randwrite --bs=32k --direct=0 --size=64m --numjobs=4
364
365When fio is utilized as a basis of any reasonably large test suite, it might be
366desirable to share a set of standardized settings across multiple job files.
367Instead of copy/pasting such settings, any section may pull in an external
368:file:`filename.fio` file with *include filename* directive, as in the following
369example::
370
371 ; -- start job file including.fio --
372 [global]
373 filename=/tmp/test
374 filesize=1m
375 include glob-include.fio
376
377 [test]
378 rw=randread
379 bs=4k
380 time_based=1
381 runtime=10
382 include test-include.fio
383 ; -- end job file including.fio --
384
385.. code-block:: ini
386
387 ; -- start job file glob-include.fio --
388 thread=1
389 group_reporting=1
390 ; -- end job file glob-include.fio --
391
392.. code-block:: ini
393
394 ; -- start job file test-include.fio --
395 ioengine=libaio
396 iodepth=4
397 ; -- end job file test-include.fio --
398
399Settings pulled into a section apply to that section only (except *global*
400section). Include directives may be nested in that any included file may contain
401further include directive(s). Include files may not contain [] sections.
402
403
404Environment variables
405~~~~~~~~~~~~~~~~~~~~~
406
407Fio also supports environment variable expansion in job files. Any sub-string of
408the form ``${VARNAME}`` as part of an option value (in other words, on the right
409of the '='), will be expanded to the value of the environment variable called
410`VARNAME`. If no such environment variable is defined, or `VARNAME` is the
411empty string, the empty string will be substituted.
412
413As an example, let's look at a sample fio invocation and job file::
414
415$ SIZE=64m NUMJOBS=4 fio jobfile.fio
416
417.. code-block:: ini
418
419 ; -- start job file --
420 [random-writers]
421 rw=randwrite
422 size=${SIZE}
423 numjobs=${NUMJOBS}
424 ; -- end job file --
425
426This will expand to the following equivalent job file at runtime:
427
428.. code-block:: ini
429
430 ; -- start job file --
431 [random-writers]
432 rw=randwrite
433 size=64m
434 numjobs=4
435 ; -- end job file --
436
437Fio ships with a few example job files, you can also look there for inspiration.
438
439Reserved keywords
440~~~~~~~~~~~~~~~~~
441
442Additionally, fio has a set of reserved keywords that will be replaced
443internally with the appropriate value. Those keywords are:
444
445**$pagesize**
446
447 The architecture page size of the running system.
448
449**$mb_memory**
450
451 Megabytes of total memory in the system.
452
453**$ncpus**
454
455 Number of online available CPUs.
456
457These can be used on the command line or in the job file, and will be
458automatically substituted with the current system values when the job is
459run. Simple math is also supported on these keywords, so you can perform actions
460like::
461
b034c0dd 462 size=8*$mb_memory
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463
464and get that properly expanded to 8 times the size of memory in the machine.
465
466
467Job file parameters
468-------------------
469
470This section describes in details each parameter associated with a job. Some
471parameters take an option of a given type, such as an integer or a
472string. Anywhere a numeric value is required, an arithmetic expression may be
473used, provided it is surrounded by parentheses. Supported operators are:
474
475 - addition (+)
476 - subtraction (-)
477 - multiplication (*)
478 - division (/)
479 - modulus (%)
480 - exponentiation (^)
481
482For time values in expressions, units are microseconds by default. This is
483different than for time values not in expressions (not enclosed in
484parentheses). The following types are used:
485
486
487Parameter types
488~~~~~~~~~~~~~~~
489
490**str**
b034c0dd 491 String: A sequence of alphanumeric characters.
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492
493**time**
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494 Integer with possible time suffix. Without a unit value is interpreted as
495 seconds unless otherwise specified. Accepts a suffix of 'd' for days, 'h' for
496 hours, 'm' for minutes, 's' for seconds, 'ms' (or 'msec') for milliseconds and
497 'us' (or 'usec') for microseconds. For example, use 10m for 10 minutes.
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498
499.. _int:
500
501**int**
502 Integer. A whole number value, which may contain an integer prefix
503 and an integer suffix:
504
b034c0dd 505 [*integer prefix*] **number** [*integer suffix*]
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506
507 The optional *integer prefix* specifies the number's base. The default
508 is decimal. *0x* specifies hexadecimal.
509
510 The optional *integer suffix* specifies the number's units, and includes an
511 optional unit prefix and an optional unit. For quantities of data, the
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512 default unit is bytes. For quantities of time, the default unit is seconds
513 unless otherwise specified.
f80dba8d 514
9207a0cb 515 With :option:`kb_base`\=1000, fio follows international standards for unit
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516 prefixes. To specify power-of-10 decimal values defined in the
517 International System of Units (SI):
518
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519 * *K* -- means kilo (K) or 1000
520 * *M* -- means mega (M) or 1000**2
521 * *G* -- means giga (G) or 1000**3
522 * *T* -- means tera (T) or 1000**4
523 * *P* -- means peta (P) or 1000**5
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524
525 To specify power-of-2 binary values defined in IEC 80000-13:
526
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527 * *Ki* -- means kibi (Ki) or 1024
528 * *Mi* -- means mebi (Mi) or 1024**2
529 * *Gi* -- means gibi (Gi) or 1024**3
530 * *Ti* -- means tebi (Ti) or 1024**4
531 * *Pi* -- means pebi (Pi) or 1024**5
f80dba8d 532
9207a0cb 533 With :option:`kb_base`\=1024 (the default), the unit prefixes are opposite
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534 from those specified in the SI and IEC 80000-13 standards to provide
535 compatibility with old scripts. For example, 4k means 4096.
536
537 For quantities of data, an optional unit of 'B' may be included
b8f7e412 538 (e.g., 'kB' is the same as 'k').
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539
540 The *integer suffix* is not case sensitive (e.g., m/mi mean mebi/mega,
541 not milli). 'b' and 'B' both mean byte, not bit.
542
9207a0cb 543 Examples with :option:`kb_base`\=1000:
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544
545 * *4 KiB*: 4096, 4096b, 4096B, 4ki, 4kib, 4kiB, 4Ki, 4KiB
546 * *1 MiB*: 1048576, 1mi, 1024ki
547 * *1 MB*: 1000000, 1m, 1000k
548 * *1 TiB*: 1099511627776, 1ti, 1024gi, 1048576mi
549 * *1 TB*: 1000000000, 1t, 1000m, 1000000k
550
9207a0cb 551 Examples with :option:`kb_base`\=1024 (default):
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552
553 * *4 KiB*: 4096, 4096b, 4096B, 4k, 4kb, 4kB, 4K, 4KB
554 * *1 MiB*: 1048576, 1m, 1024k
555 * *1 MB*: 1000000, 1mi, 1000ki
556 * *1 TiB*: 1099511627776, 1t, 1024g, 1048576m
557 * *1 TB*: 1000000000, 1ti, 1000mi, 1000000ki
558
559 To specify times (units are not case sensitive):
560
561 * *D* -- means days
562 * *H* -- means hours
4502cb42 563 * *M* -- means minutes
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564 * *s* -- or sec means seconds (default)
565 * *ms* -- or *msec* means milliseconds
566 * *us* -- or *usec* means microseconds
567
568 If the option accepts an upper and lower range, use a colon ':' or
569 minus '-' to separate such values. See :ref:`irange <irange>`.
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570 If the lower value specified happens to be larger than the upper value
571 the two values are swapped.
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572
573.. _bool:
574
575**bool**
576 Boolean. Usually parsed as an integer, however only defined for
577 true and false (1 and 0).
578
579.. _irange:
580
581**irange**
582 Integer range with suffix. Allows value range to be given, such as
c60ebc45 583 1024-4096. A colon may also be used as the separator, e.g. 1k:4k. If the
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584 option allows two sets of ranges, they can be specified with a ',' or '/'
585 delimiter: 1k-4k/8k-32k. Also see :ref:`int <int>`.
586
587**float_list**
588 A list of floating point numbers, separated by a ':' character.
589
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590With the above in mind, here follows the complete list of fio job parameters.
591
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592
593Units
594~~~~~
595
596.. option:: kb_base=int
597
598 Select the interpretation of unit prefixes in input parameters.
599
600 **1000**
601 Inputs comply with IEC 80000-13 and the International
602 System of Units (SI). Use:
603
604 - power-of-2 values with IEC prefixes (e.g., KiB)
605 - power-of-10 values with SI prefixes (e.g., kB)
606
607 **1024**
608 Compatibility mode (default). To avoid breaking old scripts:
609
610 - power-of-2 values with SI prefixes
611 - power-of-10 values with IEC prefixes
612
613 See :option:`bs` for more details on input parameters.
614
615 Outputs always use correct prefixes. Most outputs include both
616 side-by-side, like::
617
618 bw=2383.3kB/s (2327.4KiB/s)
619
620 If only one value is reported, then kb_base selects the one to use:
621
622 **1000** -- SI prefixes
623
624 **1024** -- IEC prefixes
625
626.. option:: unit_base=int
627
628 Base unit for reporting. Allowed values are:
629
630 **0**
631 Use auto-detection (default).
632 **8**
633 Byte based.
634 **1**
635 Bit based.
636
637
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638Job description
639~~~~~~~~~~~~~~~
640
641.. option:: name=str
642
643 ASCII name of the job. This may be used to override the name printed by fio
644 for this job. Otherwise the job name is used. On the command line this
645 parameter has the special purpose of also signaling the start of a new job.
646
647.. option:: description=str
648
649 Text description of the job. Doesn't do anything except dump this text
650 description when this job is run. It's not parsed.
651
652.. option:: loops=int
653
654 Run the specified number of iterations of this job. Used to repeat the same
655 workload a given number of times. Defaults to 1.
656
657.. option:: numjobs=int
658
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659 Create the specified number of clones of this job. Each clone of job
660 is spawned as an independent thread or process. May be used to setup a
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661 larger number of threads/processes doing the same thing. Each thread is
662 reported separately; to see statistics for all clones as a whole, use
663 :option:`group_reporting` in conjunction with :option:`new_group`.
a47b697c 664 See :option:`--max-jobs`. Default: 1.
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665
666
667Time related parameters
668~~~~~~~~~~~~~~~~~~~~~~~
669
670.. option:: runtime=time
671
f75ede1d 672 Tell fio to terminate processing after the specified period of time. It
f80dba8d 673 can be quite hard to determine for how long a specified job will run, so
f75ede1d 674 this parameter is handy to cap the total runtime to a given time. When
804c0839 675 the unit is omitted, the value is interpreted in seconds.
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676
677.. option:: time_based
678
679 If set, fio will run for the duration of the :option:`runtime` specified
680 even if the file(s) are completely read or written. It will simply loop over
681 the same workload as many times as the :option:`runtime` allows.
682
a881438b 683.. option:: startdelay=irange(time)
f80dba8d 684
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685 Delay the start of job for the specified amount of time. Can be a single
686 value or a range. When given as a range, each thread will choose a value
687 randomly from within the range. Value is in seconds if a unit is omitted.
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688
689.. option:: ramp_time=time
690
691 If set, fio will run the specified workload for this amount of time before
692 logging any performance numbers. Useful for letting performance settle
693 before logging results, thus minimizing the runtime required for stable
694 results. Note that the ``ramp_time`` is considered lead in time for a job,
695 thus it will increase the total runtime if a special timeout or
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696 :option:`runtime` is specified. When the unit is omitted, the value is
697 given in seconds.
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698
699.. option:: clocksource=str
700
701 Use the given clocksource as the base of timing. The supported options are:
702
703 **gettimeofday**
704 :manpage:`gettimeofday(2)`
705
706 **clock_gettime**
707 :manpage:`clock_gettime(2)`
708
709 **cpu**
710 Internal CPU clock source
711
712 cpu is the preferred clocksource if it is reliable, as it is very fast (and
713 fio is heavy on time calls). Fio will automatically use this clocksource if
714 it's supported and considered reliable on the system it is running on,
715 unless another clocksource is specifically set. For x86/x86-64 CPUs, this
716 means supporting TSC Invariant.
717
718.. option:: gtod_reduce=bool
719
720 Enable all of the :manpage:`gettimeofday(2)` reducing options
f75ede1d 721 (:option:`disable_clat`, :option:`disable_slat`, :option:`disable_bw_measurement`) plus
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722 reduce precision of the timeout somewhat to really shrink the
723 :manpage:`gettimeofday(2)` call count. With this option enabled, we only do
724 about 0.4% of the :manpage:`gettimeofday(2)` calls we would have done if all
725 time keeping was enabled.
726
727.. option:: gtod_cpu=int
728
729 Sometimes it's cheaper to dedicate a single thread of execution to just
730 getting the current time. Fio (and databases, for instance) are very
731 intensive on :manpage:`gettimeofday(2)` calls. With this option, you can set
732 one CPU aside for doing nothing but logging current time to a shared memory
733 location. Then the other threads/processes that run I/O workloads need only
734 copy that segment, instead of entering the kernel with a
735 :manpage:`gettimeofday(2)` call. The CPU set aside for doing these time
736 calls will be excluded from other uses. Fio will manually clear it from the
737 CPU mask of other jobs.
738
739
740Target file/device
741~~~~~~~~~~~~~~~~~~
742
743.. option:: directory=str
744
745 Prefix filenames with this directory. Used to place files in a different
746 location than :file:`./`. You can specify a number of directories by
747 separating the names with a ':' character. These directories will be
02dd2689 748 assigned equally distributed to job clones created by :option:`numjobs` as
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749 long as they are using generated filenames. If specific `filename(s)` are
750 set fio will use the first listed directory, and thereby matching the
751 `filename` semantic which generates a file each clone if not specified, but
752 let all clones use the same if set.
753
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754 See the :option:`filename` option for information on how to escape "``:``" and
755 "``\``" characters within the directory path itself.
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756
757.. option:: filename=str
758
759 Fio normally makes up a `filename` based on the job name, thread number, and
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760 file number (see :option:`filename_format`). If you want to share files
761 between threads in a job or several
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762 jobs with fixed file paths, specify a `filename` for each of them to override
763 the default. If the ioengine is file based, you can specify a number of files
764 by separating the names with a ':' colon. So if you wanted a job to open
765 :file:`/dev/sda` and :file:`/dev/sdb` as the two working files, you would use
766 ``filename=/dev/sda:/dev/sdb``. This also means that whenever this option is
767 specified, :option:`nrfiles` is ignored. The size of regular files specified
02dd2689 768 by this option will be :option:`size` divided by number of files unless an
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769 explicit size is specified by :option:`filesize`.
770
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771 Each colon and backslash in the wanted path must be escaped with a ``\``
772 character. For instance, if the path is :file:`/dev/dsk/foo@3,0:c` then you
773 would use ``filename=/dev/dsk/foo@3,0\:c`` and if the path is
774 :file:`F:\\filename` then you would use ``filename=F\:\\filename``.
775
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776 On Windows, disk devices are accessed as :file:`\\\\.\\PhysicalDrive0` for
777 the first device, :file:`\\\\.\\PhysicalDrive1` for the second etc.
778 Note: Windows and FreeBSD prevent write access to areas
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779 of the disk containing in-use data (e.g. filesystems).
780
781 The filename "`-`" is a reserved name, meaning *stdin* or *stdout*. Which
782 of the two depends on the read/write direction set.
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783
784.. option:: filename_format=str
785
786 If sharing multiple files between jobs, it is usually necessary to have fio
787 generate the exact names that you want. By default, fio will name a file
788 based on the default file format specification of
789 :file:`jobname.jobnumber.filenumber`. With this option, that can be
790 customized. Fio will recognize and replace the following keywords in this
791 string:
792
793 **$jobname**
794 The name of the worker thread or process.
795 **$jobnum**
796 The incremental number of the worker thread or process.
797 **$filenum**
798 The incremental number of the file for that worker thread or
799 process.
800
801 To have dependent jobs share a set of files, this option can be set to have
802 fio generate filenames that are shared between the two. For instance, if
803 :file:`testfiles.$filenum` is specified, file number 4 for any job will be
804 named :file:`testfiles.4`. The default of :file:`$jobname.$jobnum.$filenum`
805 will be used if no other format specifier is given.
806
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807 If you specify a path then the directories will be created up to the
808 main directory for the file. So for example if you specify
809 ``filename_format=a/b/c/$jobnum`` then the directories a/b/c will be
810 created before the file setup part of the job. If you specify
811 :option:`directory` then the path will be relative that directory,
812 otherwise it is treated as the absolute path.
813
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814.. option:: unique_filename=bool
815
816 To avoid collisions between networked clients, fio defaults to prefixing any
817 generated filenames (with a directory specified) with the source of the
818 client connecting. To disable this behavior, set this option to 0.
819
820.. option:: opendir=str
821
822 Recursively open any files below directory `str`.
823
824.. option:: lockfile=str
825
826 Fio defaults to not locking any files before it does I/O to them. If a file
827 or file descriptor is shared, fio can serialize I/O to that file to make the
828 end result consistent. This is usual for emulating real workloads that share
829 files. The lock modes are:
830
831 **none**
832 No locking. The default.
833 **exclusive**
834 Only one thread or process may do I/O at a time, excluding all
835 others.
836 **readwrite**
837 Read-write locking on the file. Many readers may
838 access the file at the same time, but writes get exclusive access.
839
840.. option:: nrfiles=int
841
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842 Number of files to use for this job. Defaults to 1. The size of files
843 will be :option:`size` divided by this unless explicit size is specified by
844 :option:`filesize`. Files are created for each thread separately, and each
845 file will have a file number within its name by default, as explained in
846 :option:`filename` section.
847
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848
849.. option:: openfiles=int
850
851 Number of files to keep open at the same time. Defaults to the same as
852 :option:`nrfiles`, can be set smaller to limit the number simultaneous
853 opens.
854
855.. option:: file_service_type=str
856
857 Defines how fio decides which file from a job to service next. The following
858 types are defined:
859
860 **random**
861 Choose a file at random.
862
863 **roundrobin**
864 Round robin over opened files. This is the default.
865
866 **sequential**
867 Finish one file before moving on to the next. Multiple files can
f50fbdda 868 still be open depending on :option:`openfiles`.
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869
870 **zipf**
c60ebc45 871 Use a *Zipf* distribution to decide what file to access.
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872
873 **pareto**
c60ebc45 874 Use a *Pareto* distribution to decide what file to access.
f80dba8d 875
dd3503d3 876 **normal**
c60ebc45 877 Use a *Gaussian* (normal) distribution to decide what file to
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878 access.
879
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880 **gauss**
881 Alias for normal.
882
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883 For *random*, *roundrobin*, and *sequential*, a postfix can be appended to
884 tell fio how many I/Os to issue before switching to a new file. For example,
885 specifying ``file_service_type=random:8`` would cause fio to issue
886 8 I/Os before selecting a new file at random. For the non-uniform
887 distributions, a floating point postfix can be given to influence how the
888 distribution is skewed. See :option:`random_distribution` for a description
889 of how that would work.
890
891.. option:: ioscheduler=str
892
893 Attempt to switch the device hosting the file to the specified I/O scheduler
894 before running.
895
896.. option:: create_serialize=bool
897
898 If true, serialize the file creation for the jobs. This may be handy to
899 avoid interleaving of data files, which may greatly depend on the filesystem
a47b697c 900 used and even the number of processors in the system. Default: true.
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901
902.. option:: create_fsync=bool
903
22413915 904 :manpage:`fsync(2)` the data file after creation. This is the default.
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905
906.. option:: create_on_open=bool
907
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908 If true, don't pre-create files but allow the job's open() to create a file
909 when it's time to do I/O. Default: false -- pre-create all necessary files
910 when the job starts.
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911
912.. option:: create_only=bool
913
914 If true, fio will only run the setup phase of the job. If files need to be
4502cb42 915 laid out or updated on disk, only that will be done -- the actual job contents
a47b697c 916 are not executed. Default: false.
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917
918.. option:: allow_file_create=bool
919
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920 If true, fio is permitted to create files as part of its workload. If this
921 option is false, then fio will error out if
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922 the files it needs to use don't already exist. Default: true.
923
924.. option:: allow_mounted_write=bool
925
c60ebc45 926 If this isn't set, fio will abort jobs that are destructive (e.g. that write)
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927 to what appears to be a mounted device or partition. This should help catch
928 creating inadvertently destructive tests, not realizing that the test will
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929 destroy data on the mounted file system. Note that some platforms don't allow
930 writing against a mounted device regardless of this option. Default: false.
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931
932.. option:: pre_read=bool
933
934 If this is given, files will be pre-read into memory before starting the
935 given I/O operation. This will also clear the :option:`invalidate` flag,
936 since it is pointless to pre-read and then drop the cache. This will only
937 work for I/O engines that are seek-able, since they allow you to read the
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938 same data multiple times. Thus it will not work on non-seekable I/O engines
939 (e.g. network, splice). Default: false.
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940
941.. option:: unlink=bool
942
943 Unlink the job files when done. Not the default, as repeated runs of that
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944 job would then waste time recreating the file set again and again. Default:
945 false.
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946
947.. option:: unlink_each_loop=bool
948
a47b697c 949 Unlink job files after each iteration or loop. Default: false.
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950
951.. option:: zonesize=int
952
953 Divide a file into zones of the specified size. See :option:`zoneskip`.
954
955.. option:: zonerange=int
956
957 Give size of an I/O zone. See :option:`zoneskip`.
958
959.. option:: zoneskip=int
960
961 Skip the specified number of bytes when :option:`zonesize` data has been
962 read. The two zone options can be used to only do I/O on zones of a file.
963
964
965I/O type
966~~~~~~~~
967
968.. option:: direct=bool
969
970 If value is true, use non-buffered I/O. This is usually O_DIRECT. Note that
8e889110 971 OpenBSD and ZFS on Solaris don't support direct I/O. On Windows the synchronous
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972 ioengines don't support direct I/O. Default: false.
973
974.. option:: atomic=bool
975
976 If value is true, attempt to use atomic direct I/O. Atomic writes are
977 guaranteed to be stable once acknowledged by the operating system. Only
978 Linux supports O_ATOMIC right now.
979
980.. option:: buffered=bool
981
982 If value is true, use buffered I/O. This is the opposite of the
983 :option:`direct` option. Defaults to true.
984
985.. option:: readwrite=str, rw=str
986
987 Type of I/O pattern. Accepted values are:
988
989 **read**
990 Sequential reads.
991 **write**
992 Sequential writes.
993 **trim**
994 Sequential trims (Linux block devices only).
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995 **randread**
996 Random reads.
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997 **randwrite**
998 Random writes.
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999 **randtrim**
1000 Random trims (Linux block devices only).
1001 **rw,readwrite**
1002 Sequential mixed reads and writes.
1003 **randrw**
1004 Random mixed reads and writes.
1005 **trimwrite**
1006 Sequential trim+write sequences. Blocks will be trimmed first,
1007 then the same blocks will be written to.
1008
1009 Fio defaults to read if the option is not specified. For the mixed I/O
1010 types, the default is to split them 50/50. For certain types of I/O the
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1011 result may still be skewed a bit, since the speed may be different.
1012
1013 It is possible to specify the number of I/Os to do before getting a new
1014 offset by appending ``:<nr>`` to the end of the string given. For a
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1015 random read, it would look like ``rw=randread:8`` for passing in an offset
1016 modifier with a value of 8. If the suffix is used with a sequential I/O
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1017 pattern, then the *<nr>* value specified will be **added** to the generated
1018 offset for each I/O turning sequential I/O into sequential I/O with holes.
1019 For instance, using ``rw=write:4k`` will skip 4k for every write. Also see
1020 the :option:`rw_sequencer` option.
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1021
1022.. option:: rw_sequencer=str
1023
1024 If an offset modifier is given by appending a number to the ``rw=<str>``
1025 line, then this option controls how that number modifies the I/O offset
1026 being generated. Accepted values are:
1027
1028 **sequential**
1029 Generate sequential offset.
1030 **identical**
1031 Generate the same offset.
1032
1033 ``sequential`` is only useful for random I/O, where fio would normally
c60ebc45 1034 generate a new random offset for every I/O. If you append e.g. 8 to randread,
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1035 you would get a new random offset for every 8 I/Os. The result would be a
1036 seek for only every 8 I/Os, instead of for every I/O. Use ``rw=randread:8``
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1037 to specify that. As sequential I/O is already sequential, setting
1038 ``sequential`` for that would not result in any differences. ``identical``
1039 behaves in a similar fashion, except it sends the same offset 8 number of
1040 times before generating a new offset.
1041
1042.. option:: unified_rw_reporting=bool
1043
1044 Fio normally reports statistics on a per data direction basis, meaning that
1045 reads, writes, and trims are accounted and reported separately. If this
1046 option is set fio sums the results and report them as "mixed" instead.
1047
1048.. option:: randrepeat=bool
1049
1050 Seed the random number generator used for random I/O patterns in a
1051 predictable way so the pattern is repeatable across runs. Default: true.
1052
1053.. option:: allrandrepeat=bool
1054
1055 Seed all random number generators in a predictable way so results are
1056 repeatable across runs. Default: false.
1057
1058.. option:: randseed=int
1059
1060 Seed the random number generators based on this seed value, to be able to
1061 control what sequence of output is being generated. If not set, the random
1062 sequence depends on the :option:`randrepeat` setting.
1063
1064.. option:: fallocate=str
1065
1066 Whether pre-allocation is performed when laying down files.
1067 Accepted values are:
1068
1069 **none**
1070 Do not pre-allocate space.
1071
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1072 **native**
1073 Use a platform's native pre-allocation call but fall back to
1074 **none** behavior if it fails/is not implemented.
1075
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1076 **posix**
1077 Pre-allocate via :manpage:`posix_fallocate(3)`.
1078
1079 **keep**
1080 Pre-allocate via :manpage:`fallocate(2)` with
1081 FALLOC_FL_KEEP_SIZE set.
1082
1083 **0**
1084 Backward-compatible alias for **none**.
1085
1086 **1**
1087 Backward-compatible alias for **posix**.
1088
1089 May not be available on all supported platforms. **keep** is only available
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1090 on Linux. If using ZFS on Solaris this cannot be set to **posix**
1091 because ZFS doesn't support pre-allocation. Default: **native** if any
1092 pre-allocation methods are available, **none** if not.
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1093
1094.. option:: fadvise_hint=str
1095
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1096 Use :manpage:`posix_fadvise(2)` or :manpage:`posix_fadvise(2)` to
1097 advise the kernel on what I/O patterns are likely to be issued.
1098 Accepted values are:
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1099
1100 **0**
1101 Backwards-compatible hint for "no hint".
1102
1103 **1**
1104 Backwards compatible hint for "advise with fio workload type". This
1105 uses **FADV_RANDOM** for a random workload, and **FADV_SEQUENTIAL**
1106 for a sequential workload.
1107
1108 **sequential**
1109 Advise using **FADV_SEQUENTIAL**.
1110
1111 **random**
1112 Advise using **FADV_RANDOM**.
1113
8f4b9f24 1114.. option:: write_hint=str
f80dba8d 1115
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1116 Use :manpage:`fcntl(2)` to advise the kernel what life time to expect
1117 from a write. Only supported on Linux, as of version 4.13. Accepted
1118 values are:
1119
1120 **none**
1121 No particular life time associated with this file.
1122
1123 **short**
1124 Data written to this file has a short life time.
1125
1126 **medium**
1127 Data written to this file has a medium life time.
1128
1129 **long**
1130 Data written to this file has a long life time.
1131
1132 **extreme**
1133 Data written to this file has a very long life time.
1134
1135 The values are all relative to each other, and no absolute meaning
1136 should be associated with them.
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1137
1138.. option:: offset=int
1139
82dbb8cb 1140 Start I/O at the provided offset in the file, given as either a fixed size in
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1141 bytes or a percentage. If a percentage is given, the generated offset will be
1142 aligned to the minimum ``blocksize`` or to the value of ``offset_align`` if
1143 provided. Data before the given offset will not be touched. This
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1144 effectively caps the file size at `real_size - offset`. Can be combined with
1145 :option:`size` to constrain the start and end range of the I/O workload.
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1146 A percentage can be specified by a number between 1 and 100 followed by '%',
1147 for example, ``offset=20%`` to specify 20%.
f80dba8d 1148
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1149.. option:: offset_align=int
1150
1151 If set to non-zero value, the byte offset generated by a percentage ``offset``
1152 is aligned upwards to this value. Defaults to 0 meaning that a percentage
1153 offset is aligned to the minimum block size.
1154
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1155.. option:: offset_increment=int
1156
1157 If this is provided, then the real offset becomes `offset + offset_increment
1158 * thread_number`, where the thread number is a counter that starts at 0 and
1159 is incremented for each sub-job (i.e. when :option:`numjobs` option is
1160 specified). This option is useful if there are several jobs which are
1161 intended to operate on a file in parallel disjoint segments, with even
1162 spacing between the starting points.
1163
1164.. option:: number_ios=int
1165
c60ebc45 1166 Fio will normally perform I/Os until it has exhausted the size of the region
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1167 set by :option:`size`, or if it exhaust the allocated time (or hits an error
1168 condition). With this setting, the range/size can be set independently of
c60ebc45 1169 the number of I/Os to perform. When fio reaches this number, it will exit
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1170 normally and report status. Note that this does not extend the amount of I/O
1171 that will be done, it will only stop fio if this condition is met before
1172 other end-of-job criteria.
1173
1174.. option:: fsync=int
1175
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1176 If writing to a file, issue an :manpage:`fsync(2)` (or its equivalent) of
1177 the dirty data for every number of blocks given. For example, if you give 32
1178 as a parameter, fio will sync the file after every 32 writes issued. If fio is
1179 using non-buffered I/O, we may not sync the file. The exception is the sg
1180 I/O engine, which synchronizes the disk cache anyway. Defaults to 0, which
1181 means fio does not periodically issue and wait for a sync to complete. Also
1182 see :option:`end_fsync` and :option:`fsync_on_close`.
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1183
1184.. option:: fdatasync=int
1185
1186 Like :option:`fsync` but uses :manpage:`fdatasync(2)` to only sync data and
000a5f1c 1187 not metadata blocks. In Windows, FreeBSD, and DragonFlyBSD there is no
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1188 :manpage:`fdatasync(2)` so this falls back to using :manpage:`fsync(2)`.
1189 Defaults to 0, which means fio does not periodically issue and wait for a
1190 data-only sync to complete.
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1191
1192.. option:: write_barrier=int
1193
2831be97 1194 Make every `N-th` write a barrier write.
f80dba8d 1195
f50fbdda 1196.. option:: sync_file_range=str:int
f80dba8d 1197
f50fbdda 1198 Use :manpage:`sync_file_range(2)` for every `int` number of write
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1199 operations. Fio will track range of writes that have happened since the last
1200 :manpage:`sync_file_range(2)` call. `str` can currently be one or more of:
1201
1202 **wait_before**
1203 SYNC_FILE_RANGE_WAIT_BEFORE
1204 **write**
1205 SYNC_FILE_RANGE_WRITE
1206 **wait_after**
1207 SYNC_FILE_RANGE_WAIT_AFTER
1208
1209 So if you do ``sync_file_range=wait_before,write:8``, fio would use
1210 ``SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE`` for every 8
1211 writes. Also see the :manpage:`sync_file_range(2)` man page. This option is
1212 Linux specific.
1213
1214.. option:: overwrite=bool
1215
1216 If true, writes to a file will always overwrite existing data. If the file
1217 doesn't already exist, it will be created before the write phase begins. If
1218 the file exists and is large enough for the specified write phase, nothing
a47b697c 1219 will be done. Default: false.
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1220
1221.. option:: end_fsync=bool
1222
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1223 If true, :manpage:`fsync(2)` file contents when a write stage has completed.
1224 Default: false.
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1225
1226.. option:: fsync_on_close=bool
1227
1228 If true, fio will :manpage:`fsync(2)` a dirty file on close. This differs
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1229 from :option:`end_fsync` in that it will happen on every file close, not
1230 just at the end of the job. Default: false.
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1231
1232.. option:: rwmixread=int
1233
1234 Percentage of a mixed workload that should be reads. Default: 50.
1235
1236.. option:: rwmixwrite=int
1237
1238 Percentage of a mixed workload that should be writes. If both
1239 :option:`rwmixread` and :option:`rwmixwrite` is given and the values do not
1240 add up to 100%, the latter of the two will be used to override the
1241 first. This may interfere with a given rate setting, if fio is asked to
1242 limit reads or writes to a certain rate. If that is the case, then the
1243 distribution may be skewed. Default: 50.
1244
1245.. option:: random_distribution=str:float[,str:float][,str:float]
1246
1247 By default, fio will use a completely uniform random distribution when asked
1248 to perform random I/O. Sometimes it is useful to skew the distribution in
1249 specific ways, ensuring that some parts of the data is more hot than others.
1250 fio includes the following distribution models:
1251
1252 **random**
1253 Uniform random distribution
1254
1255 **zipf**
1256 Zipf distribution
1257
1258 **pareto**
1259 Pareto distribution
1260
b2f4b559 1261 **normal**
c60ebc45 1262 Normal (Gaussian) distribution
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1263
1264 **zoned**
1265 Zoned random distribution
1266
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1267 **zoned_abs**
1268 Zone absolute random distribution
1269
f80dba8d 1270 When using a **zipf** or **pareto** distribution, an input value is also
f50fbdda 1271 needed to define the access pattern. For **zipf**, this is the `Zipf
c60ebc45 1272 theta`. For **pareto**, it's the `Pareto power`. Fio includes a test
f50fbdda 1273 program, :command:`fio-genzipf`, that can be used visualize what the given input
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1274 values will yield in terms of hit rates. If you wanted to use **zipf** with
1275 a `theta` of 1.2, you would use ``random_distribution=zipf:1.2`` as the
1276 option. If a non-uniform model is used, fio will disable use of the random
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1277 map. For the **normal** distribution, a normal (Gaussian) deviation is
1278 supplied as a value between 0 and 100.
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1279
1280 For a **zoned** distribution, fio supports specifying percentages of I/O
1281 access that should fall within what range of the file or device. For
1282 example, given a criteria of:
1283
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1284 * 60% of accesses should be to the first 10%
1285 * 30% of accesses should be to the next 20%
1286 * 8% of accesses should be to the next 30%
1287 * 2% of accesses should be to the next 40%
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1288
1289 we can define that through zoning of the random accesses. For the above
1290 example, the user would do::
1291
1292 random_distribution=zoned:60/10:30/20:8/30:2/40
1293
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1294 A **zoned_abs** distribution works exactly like the **zoned**, except
1295 that it takes absolute sizes. For example, let's say you wanted to
1296 define access according to the following criteria:
1297
1298 * 60% of accesses should be to the first 20G
1299 * 30% of accesses should be to the next 100G
1300 * 10% of accesses should be to the next 500G
1301
1302 we can define an absolute zoning distribution with:
1303
1304 random_distribution=zoned_abs=60/20G:30/100G:10/500g
1305
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1306 For both **zoned** and **zoned_abs**, fio supports defining up to
1307 256 separate zones.
1308
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1309 Similarly to how :option:`bssplit` works for setting ranges and
1310 percentages of block sizes. Like :option:`bssplit`, it's possible to
1311 specify separate zones for reads, writes, and trims. If just one set
1312 is given, it'll apply to all of them. This goes for both **zoned**
1313 **zoned_abs** distributions.
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1314
1315.. option:: percentage_random=int[,int][,int]
1316
1317 For a random workload, set how big a percentage should be random. This
1318 defaults to 100%, in which case the workload is fully random. It can be set
1319 from anywhere from 0 to 100. Setting it to 0 would make the workload fully
1320 sequential. Any setting in between will result in a random mix of sequential
1321 and random I/O, at the given percentages. Comma-separated values may be
1322 specified for reads, writes, and trims as described in :option:`blocksize`.
1323
1324.. option:: norandommap
1325
1326 Normally fio will cover every block of the file when doing random I/O. If
1327 this option is given, fio will just get a new random offset without looking
1328 at past I/O history. This means that some blocks may not be read or written,
1329 and that some blocks may be read/written more than once. If this option is
1330 used with :option:`verify` and multiple blocksizes (via :option:`bsrange`),
1331 only intact blocks are verified, i.e., partially-overwritten blocks are
1332 ignored.
1333
1334.. option:: softrandommap=bool
1335
1336 See :option:`norandommap`. If fio runs with the random block map enabled and
1337 it fails to allocate the map, if this option is set it will continue without
1338 a random block map. As coverage will not be as complete as with random maps,
1339 this option is disabled by default.
1340
1341.. option:: random_generator=str
1342
f50fbdda 1343 Fio supports the following engines for generating I/O offsets for random I/O:
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1344
1345 **tausworthe**
f50fbdda 1346 Strong 2^88 cycle random number generator.
f80dba8d 1347 **lfsr**
f50fbdda 1348 Linear feedback shift register generator.
f80dba8d 1349 **tausworthe64**
f50fbdda 1350 Strong 64-bit 2^258 cycle random number generator.
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1351
1352 **tausworthe** is a strong random number generator, but it requires tracking
1353 on the side if we want to ensure that blocks are only read or written
f50fbdda 1354 once. **lfsr** guarantees that we never generate the same offset twice, and
f80dba8d 1355 it's also less computationally expensive. It's not a true random generator,
f50fbdda 1356 however, though for I/O purposes it's typically good enough. **lfsr** only
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1357 works with single block sizes, not with workloads that use multiple block
1358 sizes. If used with such a workload, fio may read or write some blocks
1359 multiple times. The default value is **tausworthe**, unless the required
1360 space exceeds 2^32 blocks. If it does, then **tausworthe64** is
1361 selected automatically.
1362
1363
1364Block size
1365~~~~~~~~~~
1366
1367.. option:: blocksize=int[,int][,int], bs=int[,int][,int]
1368
1369 The block size in bytes used for I/O units. Default: 4096. A single value
1370 applies to reads, writes, and trims. Comma-separated values may be
1371 specified for reads, writes, and trims. A value not terminated in a comma
1372 applies to subsequent types.
1373
1374 Examples:
1375
1376 **bs=256k**
1377 means 256k for reads, writes and trims.
1378
1379 **bs=8k,32k**
1380 means 8k for reads, 32k for writes and trims.
1381
1382 **bs=8k,32k,**
1383 means 8k for reads, 32k for writes, and default for trims.
1384
1385 **bs=,8k**
1386 means default for reads, 8k for writes and trims.
1387
1388 **bs=,8k,**
b443ae44 1389 means default for reads, 8k for writes, and default for trims.
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1390
1391.. option:: blocksize_range=irange[,irange][,irange], bsrange=irange[,irange][,irange]
1392
1393 A range of block sizes in bytes for I/O units. The issued I/O unit will
1394 always be a multiple of the minimum size, unless
1395 :option:`blocksize_unaligned` is set.
1396
1397 Comma-separated ranges may be specified for reads, writes, and trims as
1398 described in :option:`blocksize`.
1399
1400 Example: ``bsrange=1k-4k,2k-8k``.
1401
1402.. option:: bssplit=str[,str][,str]
1403
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1404 Sometimes you want even finer grained control of the block sizes
1405 issued, not just an even split between them. This option allows you to
1406 weight various block sizes, so that you are able to define a specific
1407 amount of block sizes issued. The format for this option is::
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1408
1409 bssplit=blocksize/percentage:blocksize/percentage
1410
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1411 for as many block sizes as needed. So if you want to define a workload
1412 that has 50% 64k blocks, 10% 4k blocks, and 40% 32k blocks, you would
1413 write::
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1414
1415 bssplit=4k/10:64k/50:32k/40
1416
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1417 Ordering does not matter. If the percentage is left blank, fio will
1418 fill in the remaining values evenly. So a bssplit option like this one::
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1419
1420 bssplit=4k/50:1k/:32k/
1421
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1422 would have 50% 4k ios, and 25% 1k and 32k ios. The percentages always
1423 add up to 100, if bssplit is given a range that adds up to more, it
1424 will error out.
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1425
1426 Comma-separated values may be specified for reads, writes, and trims as
1427 described in :option:`blocksize`.
1428
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1429 If you want a workload that has 50% 2k reads and 50% 4k reads, while
1430 having 90% 4k writes and 10% 8k writes, you would specify::
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1431
1432 bssplit=2k/50:4k/50,4k/90,8k/10
1433
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1434 Fio supports defining up to 64 different weights for each data
1435 direction.
1436
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1437.. option:: blocksize_unaligned, bs_unaligned
1438
1439 If set, fio will issue I/O units with any size within
1440 :option:`blocksize_range`, not just multiples of the minimum size. This
1441 typically won't work with direct I/O, as that normally requires sector
1442 alignment.
1443
589e88b7 1444.. option:: bs_is_seq_rand=bool
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1445
1446 If this option is set, fio will use the normal read,write blocksize settings
1447 as sequential,random blocksize settings instead. Any random read or write
1448 will use the WRITE blocksize settings, and any sequential read or write will
1449 use the READ blocksize settings.
1450
1451.. option:: blockalign=int[,int][,int], ba=int[,int][,int]
1452
1453 Boundary to which fio will align random I/O units. Default:
1454 :option:`blocksize`. Minimum alignment is typically 512b for using direct
1455 I/O, though it usually depends on the hardware block size. This option is
1456 mutually exclusive with using a random map for files, so it will turn off
1457 that option. Comma-separated values may be specified for reads, writes, and
1458 trims as described in :option:`blocksize`.
1459
1460
1461Buffers and memory
1462~~~~~~~~~~~~~~~~~~
1463
1464.. option:: zero_buffers
1465
1466 Initialize buffers with all zeros. Default: fill buffers with random data.
1467
1468.. option:: refill_buffers
1469
1470 If this option is given, fio will refill the I/O buffers on every
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1471 submit. Only makes sense if :option:`zero_buffers` isn't specified,
1472 naturally. Defaults to being unset i.e., the buffer is only filled at
1473 init time and the data in it is reused when possible but if any of
1474 :option:`verify`, :option:`buffer_compress_percentage` or
1475 :option:`dedupe_percentage` are enabled then `refill_buffers` is also
1476 automatically enabled.
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1477
1478.. option:: scramble_buffers=bool
1479
1480 If :option:`refill_buffers` is too costly and the target is using data
1481 deduplication, then setting this option will slightly modify the I/O buffer
1482 contents to defeat normal de-dupe attempts. This is not enough to defeat
1483 more clever block compression attempts, but it will stop naive dedupe of
1484 blocks. Default: true.
1485
1486.. option:: buffer_compress_percentage=int
1487
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1488 If this is set, then fio will attempt to provide I/O buffer content
1489 (on WRITEs) that compresses to the specified level. Fio does this by
1490 providing a mix of random data followed by fixed pattern data. The
1491 fixed pattern is either zeros, or the pattern specified by
1492 :option:`buffer_pattern`. If the `buffer_pattern` option is used, it
1493 might skew the compression ratio slightly. Setting
1494 `buffer_compress_percentage` to a value other than 100 will also
1495 enable :option:`refill_buffers` in order to reduce the likelihood that
1496 adjacent blocks are so similar that they over compress when seen
1497 together. See :option:`buffer_compress_chunk` for how to set a finer or
1498 coarser granularity for the random/fixed data region. Defaults to unset
1499 i.e., buffer data will not adhere to any compression level.
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1500
1501.. option:: buffer_compress_chunk=int
1502
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1503 This setting allows fio to manage how big the random/fixed data region
1504 is when using :option:`buffer_compress_percentage`. When
1505 `buffer_compress_chunk` is set to some non-zero value smaller than the
1506 block size, fio can repeat the random/fixed region throughout the I/O
1507 buffer at the specified interval (which particularly useful when
1508 bigger block sizes are used for a job). When set to 0, fio will use a
1509 chunk size that matches the block size resulting in a single
1510 random/fixed region within the I/O buffer. Defaults to 512. When the
1511 unit is omitted, the value is interpreted in bytes.
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1512
1513.. option:: buffer_pattern=str
1514
a1554f65
SB
1515 If set, fio will fill the I/O buffers with this pattern or with the contents
1516 of a file. If not set, the contents of I/O buffers are defined by the other
1517 options related to buffer contents. The setting can be any pattern of bytes,
1518 and can be prefixed with 0x for hex values. It may also be a string, where
1519 the string must then be wrapped with ``""``. Or it may also be a filename,
1520 where the filename must be wrapped with ``''`` in which case the file is
1521 opened and read. Note that not all the file contents will be read if that
1522 would cause the buffers to overflow. So, for example::
1523
1524 buffer_pattern='filename'
1525
1526 or::
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1527
1528 buffer_pattern="abcd"
1529
1530 or::
1531
1532 buffer_pattern=-12
1533
1534 or::
1535
1536 buffer_pattern=0xdeadface
1537
1538 Also you can combine everything together in any order::
1539
a1554f65 1540 buffer_pattern=0xdeadface"abcd"-12'filename'
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1541
1542.. option:: dedupe_percentage=int
1543
1544 If set, fio will generate this percentage of identical buffers when
1545 writing. These buffers will be naturally dedupable. The contents of the
1546 buffers depend on what other buffer compression settings have been set. It's
1547 possible to have the individual buffers either fully compressible, or not at
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1548 all -- this option only controls the distribution of unique buffers. Setting
1549 this option will also enable :option:`refill_buffers` to prevent every buffer
1550 being identical.
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1551
1552.. option:: invalidate=bool
1553
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1554 Invalidate the buffer/page cache parts of the files to be used prior to
1555 starting I/O if the platform and file type support it. Defaults to true.
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1556 This will be ignored if :option:`pre_read` is also specified for the
1557 same job.
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1558
1559.. option:: sync=bool
1560
1561 Use synchronous I/O for buffered writes. For the majority of I/O engines,
1562 this means using O_SYNC. Default: false.
1563
1564.. option:: iomem=str, mem=str
1565
1566 Fio can use various types of memory as the I/O unit buffer. The allowed
1567 values are:
1568
1569 **malloc**
1570 Use memory from :manpage:`malloc(3)` as the buffers. Default memory
1571 type.
1572
1573 **shm**
1574 Use shared memory as the buffers. Allocated through
1575 :manpage:`shmget(2)`.
1576
1577 **shmhuge**
1578 Same as shm, but use huge pages as backing.
1579
1580 **mmap**
22413915 1581 Use :manpage:`mmap(2)` to allocate buffers. May either be anonymous memory, or can
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1582 be file backed if a filename is given after the option. The format
1583 is `mem=mmap:/path/to/file`.
1584
1585 **mmaphuge**
1586 Use a memory mapped huge file as the buffer backing. Append filename
1587 after mmaphuge, ala `mem=mmaphuge:/hugetlbfs/file`.
1588
1589 **mmapshared**
1590 Same as mmap, but use a MMAP_SHARED mapping.
1591
03553853
YR
1592 **cudamalloc**
1593 Use GPU memory as the buffers for GPUDirect RDMA benchmark.
f50fbdda 1594 The :option:`ioengine` must be `rdma`.
03553853 1595
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1596 The area allocated is a function of the maximum allowed bs size for the job,
1597 multiplied by the I/O depth given. Note that for **shmhuge** and
1598 **mmaphuge** to work, the system must have free huge pages allocated. This
1599 can normally be checked and set by reading/writing
1600 :file:`/proc/sys/vm/nr_hugepages` on a Linux system. Fio assumes a huge page
1601 is 4MiB in size. So to calculate the number of huge pages you need for a
1602 given job file, add up the I/O depth of all jobs (normally one unless
1603 :option:`iodepth` is used) and multiply by the maximum bs set. Then divide
1604 that number by the huge page size. You can see the size of the huge pages in
1605 :file:`/proc/meminfo`. If no huge pages are allocated by having a non-zero
1606 number in `nr_hugepages`, using **mmaphuge** or **shmhuge** will fail. Also
1607 see :option:`hugepage-size`.
1608
1609 **mmaphuge** also needs to have hugetlbfs mounted and the file location
1610 should point there. So if it's mounted in :file:`/huge`, you would use
1611 `mem=mmaphuge:/huge/somefile`.
1612
f50fbdda 1613.. option:: iomem_align=int, mem_align=int
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1614
1615 This indicates the memory alignment of the I/O memory buffers. Note that
1616 the given alignment is applied to the first I/O unit buffer, if using
1617 :option:`iodepth` the alignment of the following buffers are given by the
1618 :option:`bs` used. In other words, if using a :option:`bs` that is a
1619 multiple of the page sized in the system, all buffers will be aligned to
1620 this value. If using a :option:`bs` that is not page aligned, the alignment
1621 of subsequent I/O memory buffers is the sum of the :option:`iomem_align` and
1622 :option:`bs` used.
1623
1624.. option:: hugepage-size=int
1625
1626 Defines the size of a huge page. Must at least be equal to the system
1627 setting, see :file:`/proc/meminfo`. Defaults to 4MiB. Should probably
1628 always be a multiple of megabytes, so using ``hugepage-size=Xm`` is the
1629 preferred way to set this to avoid setting a non-pow-2 bad value.
1630
1631.. option:: lockmem=int
1632
1633 Pin the specified amount of memory with :manpage:`mlock(2)`. Can be used to
1634 simulate a smaller amount of memory. The amount specified is per worker.
1635
1636
1637I/O size
1638~~~~~~~~
1639
1640.. option:: size=int
1641
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1642 The total size of file I/O for each thread of this job. Fio will run until
1643 this many bytes has been transferred, unless runtime is limited by other options
1644 (such as :option:`runtime`, for instance, or increased/decreased by :option:`io_size`).
1645 Fio will divide this size between the available files determined by options
1646 such as :option:`nrfiles`, :option:`filename`, unless :option:`filesize` is
1647 specified by the job. If the result of division happens to be 0, the size is
c4aa2d08 1648 set to the physical size of the given files or devices if they exist.
79591fa9 1649 If this option is not specified, fio will use the full size of the given
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1650 files or devices. If the files do not exist, size must be given. It is also
1651 possible to give size as a percentage between 1 and 100. If ``size=20%`` is
1652 given, fio will use 20% of the full size of the given files or devices.
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1653 Can be combined with :option:`offset` to constrain the start and end range
1654 that I/O will be done within.
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1655
1656.. option:: io_size=int, io_limit=int
1657
1658 Normally fio operates within the region set by :option:`size`, which means
1659 that the :option:`size` option sets both the region and size of I/O to be
1660 performed. Sometimes that is not what you want. With this option, it is
1661 possible to define just the amount of I/O that fio should do. For instance,
1662 if :option:`size` is set to 20GiB and :option:`io_size` is set to 5GiB, fio
1663 will perform I/O within the first 20GiB but exit when 5GiB have been
1664 done. The opposite is also possible -- if :option:`size` is set to 20GiB,
1665 and :option:`io_size` is set to 40GiB, then fio will do 40GiB of I/O within
1666 the 0..20GiB region.
1667
7fdd97ca 1668.. option:: filesize=irange(int)
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1669
1670 Individual file sizes. May be a range, in which case fio will select sizes
1671 for files at random within the given range and limited to :option:`size` in
1672 total (if that is given). If not given, each created file is the same size.
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1673 This option overrides :option:`size` in terms of file size, which means
1674 this value is used as a fixed size or possible range of each file.
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1675
1676.. option:: file_append=bool
1677
1678 Perform I/O after the end of the file. Normally fio will operate within the
1679 size of a file. If this option is set, then fio will append to the file
1680 instead. This has identical behavior to setting :option:`offset` to the size
1681 of a file. This option is ignored on non-regular files.
1682
1683.. option:: fill_device=bool, fill_fs=bool
1684
1685 Sets size to something really large and waits for ENOSPC (no space left on
1686 device) as the terminating condition. Only makes sense with sequential
1687 write. For a read workload, the mount point will be filled first then I/O
1688 started on the result. This option doesn't make sense if operating on a raw
1689 device node, since the size of that is already known by the file system.
1690 Additionally, writing beyond end-of-device will not return ENOSPC there.
1691
1692
1693I/O engine
1694~~~~~~~~~~
1695
1696.. option:: ioengine=str
1697
1698 Defines how the job issues I/O to the file. The following types are defined:
1699
1700 **sync**
1701 Basic :manpage:`read(2)` or :manpage:`write(2)`
1702 I/O. :manpage:`lseek(2)` is used to position the I/O location.
54227e6b 1703 See :option:`fsync` and :option:`fdatasync` for syncing write I/Os.
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1704
1705 **psync**
1706 Basic :manpage:`pread(2)` or :manpage:`pwrite(2)` I/O. Default on
1707 all supported operating systems except for Windows.
1708
1709 **vsync**
1710 Basic :manpage:`readv(2)` or :manpage:`writev(2)` I/O. Will emulate
c60ebc45 1711 queuing by coalescing adjacent I/Os into a single submission.
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1712
1713 **pvsync**
1714 Basic :manpage:`preadv(2)` or :manpage:`pwritev(2)` I/O.
1715
1716 **pvsync2**
1717 Basic :manpage:`preadv2(2)` or :manpage:`pwritev2(2)` I/O.
1718
1719 **libaio**
1720 Linux native asynchronous I/O. Note that Linux may only support
22413915 1721 queued behavior with non-buffered I/O (set ``direct=1`` or
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1722 ``buffered=0``).
1723 This engine defines engine specific options.
1724
1725 **posixaio**
1726 POSIX asynchronous I/O using :manpage:`aio_read(3)` and
1727 :manpage:`aio_write(3)`.
1728
1729 **solarisaio**
1730 Solaris native asynchronous I/O.
1731
1732 **windowsaio**
1733 Windows native asynchronous I/O. Default on Windows.
1734
1735 **mmap**
1736 File is memory mapped with :manpage:`mmap(2)` and data copied
1737 to/from using :manpage:`memcpy(3)`.
1738
1739 **splice**
1740 :manpage:`splice(2)` is used to transfer the data and
1741 :manpage:`vmsplice(2)` to transfer data from user space to the
1742 kernel.
1743
1744 **sg**
1745 SCSI generic sg v3 I/O. May either be synchronous using the SG_IO
1746 ioctl, or if the target is an sg character device we use
1747 :manpage:`read(2)` and :manpage:`write(2)` for asynchronous
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1748 I/O. Requires :option:`filename` option to specify either block or
1749 character devices.
52b81b7c 1750 The sg engine includes engine specific options.
f80dba8d
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1751
1752 **null**
1753 Doesn't transfer any data, just pretends to. This is mainly used to
1754 exercise fio itself and for debugging/testing purposes.
1755
1756 **net**
1757 Transfer over the network to given ``host:port``. Depending on the
1758 :option:`protocol` used, the :option:`hostname`, :option:`port`,
1759 :option:`listen` and :option:`filename` options are used to specify
1760 what sort of connection to make, while the :option:`protocol` option
1761 determines which protocol will be used. This engine defines engine
1762 specific options.
1763
1764 **netsplice**
1765 Like **net**, but uses :manpage:`splice(2)` and
1766 :manpage:`vmsplice(2)` to map data and send/receive.
1767 This engine defines engine specific options.
1768
1769 **cpuio**
1770 Doesn't transfer any data, but burns CPU cycles according to the
1771 :option:`cpuload` and :option:`cpuchunks` options. Setting
9207a0cb 1772 :option:`cpuload`\=85 will cause that job to do nothing but burn 85%
71aa48eb 1773 of the CPU. In case of SMP machines, use :option:`numjobs`\=<nr_of_cpu>
f50fbdda 1774 to get desired CPU usage, as the cpuload only loads a
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1775 single CPU at the desired rate. A job never finishes unless there is
1776 at least one non-cpuio job.
1777
1778 **guasi**
804c0839 1779 The GUASI I/O engine is the Generic Userspace Asynchronous Syscall
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1780 Interface approach to async I/O. See
1781
1782 http://www.xmailserver.org/guasi-lib.html
1783
1784 for more info on GUASI.
1785
1786 **rdma**
1787 The RDMA I/O engine supports both RDMA memory semantics
1788 (RDMA_WRITE/RDMA_READ) and channel semantics (Send/Recv) for the
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1789 InfiniBand, RoCE and iWARP protocols. This engine defines engine
1790 specific options.
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1791
1792 **falloc**
1793 I/O engine that does regular fallocate to simulate data transfer as
1794 fio ioengine.
1795
1796 DDIR_READ
1797 does fallocate(,mode = FALLOC_FL_KEEP_SIZE,).
1798
1799 DDIR_WRITE
1800 does fallocate(,mode = 0).
1801
1802 DDIR_TRIM
1803 does fallocate(,mode = FALLOC_FL_KEEP_SIZE|FALLOC_FL_PUNCH_HOLE).
1804
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1805 **ftruncate**
1806 I/O engine that sends :manpage:`ftruncate(2)` operations in response
1807 to write (DDIR_WRITE) events. Each ftruncate issued sets the file's
f50fbdda 1808 size to the current block offset. :option:`blocksize` is ignored.
761cd093 1809
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1810 **e4defrag**
1811 I/O engine that does regular EXT4_IOC_MOVE_EXT ioctls to simulate
1812 defragment activity in request to DDIR_WRITE event.
1813
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1814 **rados**
1815 I/O engine supporting direct access to Ceph Reliable Autonomic
1816 Distributed Object Store (RADOS) via librados. This ioengine
1817 defines engine specific options.
1818
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1819 **rbd**
1820 I/O engine supporting direct access to Ceph Rados Block Devices
1821 (RBD) via librbd without the need to use the kernel rbd driver. This
1822 ioengine defines engine specific options.
1823
1824 **gfapi**
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1825 Using GlusterFS libgfapi sync interface to direct access to
1826 GlusterFS volumes without having to go through FUSE. This ioengine
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1827 defines engine specific options.
1828
1829 **gfapi_async**
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1830 Using GlusterFS libgfapi async interface to direct access to
1831 GlusterFS volumes without having to go through FUSE. This ioengine
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1832 defines engine specific options.
1833
1834 **libhdfs**
f50fbdda 1835 Read and write through Hadoop (HDFS). The :option:`filename` option
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1836 is used to specify host,port of the hdfs name-node to connect. This
1837 engine interprets offsets a little differently. In HDFS, files once
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1838 created cannot be modified so random writes are not possible. To
1839 imitate this the libhdfs engine expects a bunch of small files to be
1840 created over HDFS and will randomly pick a file from them
1841 based on the offset generated by fio backend (see the example
f80dba8d 1842 job file to create such files, use ``rw=write`` option). Please
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1843 note, it may be necessary to set environment variables to work
1844 with HDFS/libhdfs properly. Each job uses its own connection to
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1845 HDFS.
1846
1847 **mtd**
1848 Read, write and erase an MTD character device (e.g.,
1849 :file:`/dev/mtd0`). Discards are treated as erases. Depending on the
1850 underlying device type, the I/O may have to go in a certain pattern,
1851 e.g., on NAND, writing sequentially to erase blocks and discarding
c298ee71 1852 before overwriting. The `trimwrite` mode works well for this
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1853 constraint.
1854
1855 **pmemblk**
1856 Read and write using filesystem DAX to a file on a filesystem
1857 mounted with DAX on a persistent memory device through the NVML
1858 libpmemblk library.
1859
1860 **dev-dax**
1861 Read and write using device DAX to a persistent memory device (e.g.,
1862 /dev/dax0.0) through the NVML libpmem library.
1863
1864 **external**
1865 Prefix to specify loading an external I/O engine object file. Append
c60ebc45 1866 the engine filename, e.g. ``ioengine=external:/tmp/foo.o`` to load
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1867 ioengine :file:`foo.o` in :file:`/tmp`. The path can be either
1868 absolute or relative. See :file:`engines/skeleton_external.c` for
1869 details of writing an external I/O engine.
f80dba8d 1870
1216cc5a 1871 **filecreate**
b71968b1 1872 Simply create the files and do no I/O to them. You still need to
1216cc5a 1873 set `filesize` so that all the accounting still occurs, but no
b71968b1 1874 actual I/O will be done other than creating the file.
f80dba8d 1875
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1876 **libpmem**
1877 Read and write using mmap I/O to a file on a filesystem
1878 mounted with DAX on a persistent memory device through the NVML
1879 libpmem library.
1880
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1881I/O engine specific parameters
1882~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1883
1884In addition, there are some parameters which are only valid when a specific
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1885:option:`ioengine` is in use. These are used identically to normal parameters,
1886with the caveat that when used on the command line, they must come after the
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1887:option:`ioengine` that defines them is selected.
1888
1889.. option:: userspace_reap : [libaio]
1890
1891 Normally, with the libaio engine in use, fio will use the
1892 :manpage:`io_getevents(2)` system call to reap newly returned events. With
1893 this flag turned on, the AIO ring will be read directly from user-space to
1894 reap events. The reaping mode is only enabled when polling for a minimum of
c60ebc45 1895 0 events (e.g. when :option:`iodepth_batch_complete` `=0`).
f80dba8d 1896
9d25d068 1897.. option:: hipri : [pvsync2]
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1898
1899 Set RWF_HIPRI on I/O, indicating to the kernel that it's of higher priority
1900 than normal.
1901
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1902.. option:: hipri_percentage : [pvsync2]
1903
f50fbdda 1904 When hipri is set this determines the probability of a pvsync2 I/O being high
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1905 priority. The default is 100%.
1906
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1907.. option:: cpuload=int : [cpuio]
1908
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1909 Attempt to use the specified percentage of CPU cycles. This is a mandatory
1910 option when using cpuio I/O engine.
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1911
1912.. option:: cpuchunks=int : [cpuio]
1913
1914 Split the load into cycles of the given time. In microseconds.
1915
1916.. option:: exit_on_io_done=bool : [cpuio]
1917
1918 Detect when I/O threads are done, then exit.
1919
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1920.. option:: namenode=str : [libhdfs]
1921
22413915 1922 The hostname or IP address of a HDFS cluster namenode to contact.
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1923
1924.. option:: port=int
1925
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1926 [libhdfs]
1927
1928 The listening port of the HFDS cluster namenode.
1929
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1930 [netsplice], [net]
1931
1932 The TCP or UDP port to bind to or connect to. If this is used with
1933 :option:`numjobs` to spawn multiple instances of the same job type, then
1934 this will be the starting port number since fio will use a range of
1935 ports.
1936
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1937 [rdma]
1938
1939 The port to use for RDMA-CM communication. This should be the same value
1940 on the client and the server side.
1941
1942.. option:: hostname=str : [netsplice] [net] [rdma]
f80dba8d 1943
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1944 The hostname or IP address to use for TCP, UDP or RDMA-CM based I/O. If the job
1945 is a TCP listener or UDP reader, the hostname is not used and must be omitted
f50fbdda 1946 unless it is a valid UDP multicast address.
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1947
1948.. option:: interface=str : [netsplice] [net]
1949
1950 The IP address of the network interface used to send or receive UDP
1951 multicast.
1952
1953.. option:: ttl=int : [netsplice] [net]
1954
1955 Time-to-live value for outgoing UDP multicast packets. Default: 1.
1956
1957.. option:: nodelay=bool : [netsplice] [net]
1958
1959 Set TCP_NODELAY on TCP connections.
1960
f50fbdda 1961.. option:: protocol=str, proto=str : [netsplice] [net]
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1962
1963 The network protocol to use. Accepted values are:
1964
1965 **tcp**
1966 Transmission control protocol.
1967 **tcpv6**
1968 Transmission control protocol V6.
1969 **udp**
1970 User datagram protocol.
1971 **udpv6**
1972 User datagram protocol V6.
1973 **unix**
1974 UNIX domain socket.
1975
1976 When the protocol is TCP or UDP, the port must also be given, as well as the
1977 hostname if the job is a TCP listener or UDP reader. For unix sockets, the
f50fbdda 1978 normal :option:`filename` option should be used and the port is invalid.
f80dba8d 1979
e9184ec1 1980.. option:: listen : [netsplice] [net]
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1981
1982 For TCP network connections, tell fio to listen for incoming connections
1983 rather than initiating an outgoing connection. The :option:`hostname` must
1984 be omitted if this option is used.
1985
e9184ec1 1986.. option:: pingpong : [netsplice] [net]
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1987
1988 Normally a network writer will just continue writing data, and a network
1989 reader will just consume packages. If ``pingpong=1`` is set, a writer will
1990 send its normal payload to the reader, then wait for the reader to send the
1991 same payload back. This allows fio to measure network latencies. The
1992 submission and completion latencies then measure local time spent sending or
1993 receiving, and the completion latency measures how long it took for the
1994 other end to receive and send back. For UDP multicast traffic
1995 ``pingpong=1`` should only be set for a single reader when multiple readers
1996 are listening to the same address.
1997
e9184ec1 1998.. option:: window_size : [netsplice] [net]
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1999
2000 Set the desired socket buffer size for the connection.
2001
e9184ec1 2002.. option:: mss : [netsplice] [net]
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2003
2004 Set the TCP maximum segment size (TCP_MAXSEG).
2005
2006.. option:: donorname=str : [e4defrag]
2007
730bd7d9 2008 File will be used as a block donor (swap extents between files).
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2009
2010.. option:: inplace=int : [e4defrag]
2011
2012 Configure donor file blocks allocation strategy:
2013
2014 **0**
2015 Default. Preallocate donor's file on init.
2016 **1**
2b455dbf 2017 Allocate space immediately inside defragment event, and free right
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2018 after event.
2019
f3f96717 2020.. option:: clustername=str : [rbd,rados]
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2021
2022 Specifies the name of the Ceph cluster.
2023
2024.. option:: rbdname=str : [rbd]
2025
2026 Specifies the name of the RBD.
2027
f3f96717 2028.. option:: pool=str : [rbd,rados]
f80dba8d 2029
f3f96717 2030 Specifies the name of the Ceph pool containing RBD or RADOS data.
f80dba8d 2031
f3f96717 2032.. option:: clientname=str : [rbd,rados]
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2033
2034 Specifies the username (without the 'client.' prefix) used to access the
2035 Ceph cluster. If the *clustername* is specified, the *clientname* shall be
2036 the full *type.id* string. If no type. prefix is given, fio will add
2037 'client.' by default.
2038
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2039.. option:: busy_poll=bool : [rbd,rados]
2040
2041 Poll store instead of waiting for completion. Usually this provides better
2042 throughput at cost of higher(up to 100%) CPU utilization.
2043
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2044.. option:: skip_bad=bool : [mtd]
2045
2046 Skip operations against known bad blocks.
2047
2048.. option:: hdfsdirectory : [libhdfs]
2049
2050 libhdfs will create chunk in this HDFS directory.
2051
2052.. option:: chunk_size : [libhdfs]
2053
2b455dbf 2054 The size of the chunk to use for each file.
f80dba8d 2055
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2056.. option:: verb=str : [rdma]
2057
2058 The RDMA verb to use on this side of the RDMA ioengine connection. Valid
2059 values are write, read, send and recv. These correspond to the equivalent
2060 RDMA verbs (e.g. write = rdma_write etc.). Note that this only needs to be
2061 specified on the client side of the connection. See the examples folder.
2062
2063.. option:: bindname=str : [rdma]
2064
2065 The name to use to bind the local RDMA-CM connection to a local RDMA device.
2066 This could be a hostname or an IPv4 or IPv6 address. On the server side this
2067 will be passed into the rdma_bind_addr() function and on the client site it
2068 will be used in the rdma_resolve_add() function. This can be useful when
2069 multiple paths exist between the client and the server or in certain loopback
2070 configurations.
f80dba8d 2071
52b81b7c
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2072.. option:: readfua=bool : [sg]
2073
2074 With readfua option set to 1, read operations include
2075 the force unit access (fua) flag. Default is 0.
2076
2077.. option:: writefua=bool : [sg]
2078
2079 With writefua option set to 1, write operations include
2080 the force unit access (fua) flag. Default is 0.
2081
2082
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2083I/O depth
2084~~~~~~~~~
2085
2086.. option:: iodepth=int
2087
2088 Number of I/O units to keep in flight against the file. Note that
2089 increasing *iodepth* beyond 1 will not affect synchronous ioengines (except
c60ebc45 2090 for small degrees when :option:`verify_async` is in use). Even async
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2091 engines may impose OS restrictions causing the desired depth not to be
2092 achieved. This may happen on Linux when using libaio and not setting
9207a0cb 2093 :option:`direct`\=1, since buffered I/O is not async on that OS. Keep an
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2094 eye on the I/O depth distribution in the fio output to verify that the
2095 achieved depth is as expected. Default: 1.
2096
2097.. option:: iodepth_batch_submit=int, iodepth_batch=int
2098
2099 This defines how many pieces of I/O to submit at once. It defaults to 1
2100 which means that we submit each I/O as soon as it is available, but can be
2101 raised to submit bigger batches of I/O at the time. If it is set to 0 the
2102 :option:`iodepth` value will be used.
2103
2104.. option:: iodepth_batch_complete_min=int, iodepth_batch_complete=int
2105
2106 This defines how many pieces of I/O to retrieve at once. It defaults to 1
2107 which means that we'll ask for a minimum of 1 I/O in the retrieval process
2108 from the kernel. The I/O retrieval will go on until we hit the limit set by
2109 :option:`iodepth_low`. If this variable is set to 0, then fio will always
2110 check for completed events before queuing more I/O. This helps reduce I/O
2111 latency, at the cost of more retrieval system calls.
2112
2113.. option:: iodepth_batch_complete_max=int
2114
2115 This defines maximum pieces of I/O to retrieve at once. This variable should
9207a0cb 2116 be used along with :option:`iodepth_batch_complete_min`\=int variable,
f80dba8d 2117 specifying the range of min and max amount of I/O which should be
730bd7d9 2118 retrieved. By default it is equal to the :option:`iodepth_batch_complete_min`
f80dba8d
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2119 value.
2120
2121 Example #1::
2122
2123 iodepth_batch_complete_min=1
2124 iodepth_batch_complete_max=<iodepth>
2125
2126 which means that we will retrieve at least 1 I/O and up to the whole
2127 submitted queue depth. If none of I/O has been completed yet, we will wait.
2128
2129 Example #2::
2130
2131 iodepth_batch_complete_min=0
2132 iodepth_batch_complete_max=<iodepth>
2133
2134 which means that we can retrieve up to the whole submitted queue depth, but
2135 if none of I/O has been completed yet, we will NOT wait and immediately exit
2136 the system call. In this example we simply do polling.
2137
2138.. option:: iodepth_low=int
2139
2140 The low water mark indicating when to start filling the queue
2141 again. Defaults to the same as :option:`iodepth`, meaning that fio will
2142 attempt to keep the queue full at all times. If :option:`iodepth` is set to
c60ebc45 2143 e.g. 16 and *iodepth_low* is set to 4, then after fio has filled the queue of
f80dba8d
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2144 16 requests, it will let the depth drain down to 4 before starting to fill
2145 it again.
2146
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2147.. option:: serialize_overlap=bool
2148
2149 Serialize in-flight I/Os that might otherwise cause or suffer from data races.
2150 When two or more I/Os are submitted simultaneously, there is no guarantee that
2151 the I/Os will be processed or completed in the submitted order. Further, if
2152 two or more of those I/Os are writes, any overlapping region between them can
2153 become indeterminate/undefined on certain storage. These issues can cause
2154 verification to fail erratically when at least one of the racing I/Os is
2155 changing data and the overlapping region has a non-zero size. Setting
2156 ``serialize_overlap`` tells fio to avoid provoking this behavior by explicitly
2157 serializing in-flight I/Os that have a non-zero overlap. Note that setting
ee21ebee 2158 this option can reduce both performance and the :option:`iodepth` achieved.
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2159 Additionally this option does not work when :option:`io_submit_mode` is set to
2160 offload. Default: false.
2161
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2162.. option:: io_submit_mode=str
2163
2164 This option controls how fio submits the I/O to the I/O engine. The default
2165 is `inline`, which means that the fio job threads submit and reap I/O
2166 directly. If set to `offload`, the job threads will offload I/O submission
2167 to a dedicated pool of I/O threads. This requires some coordination and thus
2168 has a bit of extra overhead, especially for lower queue depth I/O where it
2169 can increase latencies. The benefit is that fio can manage submission rates
2170 independently of the device completion rates. This avoids skewed latency
730bd7d9 2171 reporting if I/O gets backed up on the device side (the coordinated omission
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2172 problem).
2173
2174
2175I/O rate
2176~~~~~~~~
2177
a881438b 2178.. option:: thinktime=time
f80dba8d 2179
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2180 Stall the job for the specified period of time after an I/O has completed before issuing the
2181 next. May be used to simulate processing being done by an application.
947e0fe0 2182 When the unit is omitted, the value is interpreted in microseconds. See
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2183 :option:`thinktime_blocks` and :option:`thinktime_spin`.
2184
a881438b 2185.. option:: thinktime_spin=time
f80dba8d
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2186
2187 Only valid if :option:`thinktime` is set - pretend to spend CPU time doing
2188 something with the data received, before falling back to sleeping for the
f75ede1d 2189 rest of the period specified by :option:`thinktime`. When the unit is
947e0fe0 2190 omitted, the value is interpreted in microseconds.
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2191
2192.. option:: thinktime_blocks=int
2193
2194 Only valid if :option:`thinktime` is set - control how many blocks to issue,
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2195 before waiting :option:`thinktime` usecs. If not set, defaults to 1 which will make
2196 fio wait :option:`thinktime` usecs after every block. This effectively makes any
f80dba8d 2197 queue depth setting redundant, since no more than 1 I/O will be queued
f50fbdda 2198 before we have to complete it and do our :option:`thinktime`. In other words, this
f80dba8d 2199 setting effectively caps the queue depth if the latter is larger.
71bfa161 2200
f80dba8d 2201.. option:: rate=int[,int][,int]
71bfa161 2202
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2203 Cap the bandwidth used by this job. The number is in bytes/sec, the normal
2204 suffix rules apply. Comma-separated values may be specified for reads,
2205 writes, and trims as described in :option:`blocksize`.
71bfa161 2206
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2207 For example, using `rate=1m,500k` would limit reads to 1MiB/sec and writes to
2208 500KiB/sec. Capping only reads or writes can be done with `rate=,500k` or
2209 `rate=500k,` where the former will only limit writes (to 500KiB/sec) and the
2210 latter will only limit reads.
2211
f80dba8d 2212.. option:: rate_min=int[,int][,int]
71bfa161 2213
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2214 Tell fio to do whatever it can to maintain at least this bandwidth. Failing
2215 to meet this requirement will cause the job to exit. Comma-separated values
2216 may be specified for reads, writes, and trims as described in
2217 :option:`blocksize`.
71bfa161 2218
f80dba8d 2219.. option:: rate_iops=int[,int][,int]
71bfa161 2220
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2221 Cap the bandwidth to this number of IOPS. Basically the same as
2222 :option:`rate`, just specified independently of bandwidth. If the job is
2223 given a block size range instead of a fixed value, the smallest block size
2224 is used as the metric. Comma-separated values may be specified for reads,
2225 writes, and trims as described in :option:`blocksize`.
71bfa161 2226
f80dba8d 2227.. option:: rate_iops_min=int[,int][,int]
71bfa161 2228
f80dba8d
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2229 If fio doesn't meet this rate of I/O, it will cause the job to exit.
2230 Comma-separated values may be specified for reads, writes, and trims as
2231 described in :option:`blocksize`.
71bfa161 2232
f80dba8d 2233.. option:: rate_process=str
66c098b8 2234
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2235 This option controls how fio manages rated I/O submissions. The default is
2236 `linear`, which submits I/O in a linear fashion with fixed delays between
c60ebc45 2237 I/Os that gets adjusted based on I/O completion rates. If this is set to
f80dba8d
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2238 `poisson`, fio will submit I/O based on a more real world random request
2239 flow, known as the Poisson process
2240 (https://en.wikipedia.org/wiki/Poisson_point_process). The lambda will be
2241 10^6 / IOPS for the given workload.
71bfa161 2242
1a9bf814
JA
2243.. option:: rate_ignore_thinktime=bool
2244
2245 By default, fio will attempt to catch up to the specified rate setting,
2246 if any kind of thinktime setting was used. If this option is set, then
2247 fio will ignore the thinktime and continue doing IO at the specified
2248 rate, instead of entering a catch-up mode after thinktime is done.
2249
71bfa161 2250
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2251I/O latency
2252~~~~~~~~~~~
71bfa161 2253
a881438b 2254.. option:: latency_target=time
71bfa161 2255
f80dba8d 2256 If set, fio will attempt to find the max performance point that the given
f75ede1d 2257 workload will run at while maintaining a latency below this target. When
947e0fe0 2258 the unit is omitted, the value is interpreted in microseconds. See
f75ede1d 2259 :option:`latency_window` and :option:`latency_percentile`.
71bfa161 2260
a881438b 2261.. option:: latency_window=time
71bfa161 2262
f80dba8d 2263 Used with :option:`latency_target` to specify the sample window that the job
f75ede1d 2264 is run at varying queue depths to test the performance. When the unit is
947e0fe0 2265 omitted, the value is interpreted in microseconds.
b4692828 2266
f80dba8d 2267.. option:: latency_percentile=float
71bfa161 2268
c60ebc45 2269 The percentage of I/Os that must fall within the criteria specified by
f80dba8d 2270 :option:`latency_target` and :option:`latency_window`. If not set, this
c60ebc45 2271 defaults to 100.0, meaning that all I/Os must be equal or below to the value
f80dba8d 2272 set by :option:`latency_target`.
71bfa161 2273
a881438b 2274.. option:: max_latency=time
71bfa161 2275
f75ede1d 2276 If set, fio will exit the job with an ETIMEDOUT error if it exceeds this
947e0fe0 2277 maximum latency. When the unit is omitted, the value is interpreted in
f75ede1d 2278 microseconds.
71bfa161 2279
f80dba8d 2280.. option:: rate_cycle=int
71bfa161 2281
f80dba8d 2282 Average bandwidth for :option:`rate` and :option:`rate_min` over this number
a47b697c 2283 of milliseconds. Defaults to 1000.
71bfa161 2284
71bfa161 2285
f80dba8d
MT
2286I/O replay
2287~~~~~~~~~~
71bfa161 2288
f80dba8d 2289.. option:: write_iolog=str
c2b1e753 2290
f80dba8d
MT
2291 Write the issued I/O patterns to the specified file. See
2292 :option:`read_iolog`. Specify a separate file for each job, otherwise the
2293 iologs will be interspersed and the file may be corrupt.
c2b1e753 2294
f80dba8d 2295.. option:: read_iolog=str
71bfa161 2296
22413915 2297 Open an iolog with the specified filename and replay the I/O patterns it
f80dba8d
MT
2298 contains. This can be used to store a workload and replay it sometime
2299 later. The iolog given may also be a blktrace binary file, which allows fio
2300 to replay a workload captured by :command:`blktrace`. See
2301 :manpage:`blktrace(8)` for how to capture such logging data. For blktrace
2302 replay, the file needs to be turned into a blkparse binary data file first
2303 (``blkparse <device> -o /dev/null -d file_for_fio.bin``).
71bfa161 2304
589e88b7 2305.. option:: replay_no_stall=bool
71bfa161 2306
f80dba8d 2307 When replaying I/O with :option:`read_iolog` the default behavior is to
22413915 2308 attempt to respect the timestamps within the log and replay them with the
f80dba8d
MT
2309 appropriate delay between IOPS. By setting this variable fio will not
2310 respect the timestamps and attempt to replay them as fast as possible while
2311 still respecting ordering. The result is the same I/O pattern to a given
2312 device, but different timings.
71bfa161 2313
f80dba8d 2314.. option:: replay_redirect=str
b4692828 2315
f80dba8d
MT
2316 While replaying I/O patterns using :option:`read_iolog` the default behavior
2317 is to replay the IOPS onto the major/minor device that each IOP was recorded
2318 from. This is sometimes undesirable because on a different machine those
2319 major/minor numbers can map to a different device. Changing hardware on the
2320 same system can also result in a different major/minor mapping.
730bd7d9 2321 ``replay_redirect`` causes all I/Os to be replayed onto the single specified
f80dba8d 2322 device regardless of the device it was recorded
9207a0cb 2323 from. i.e. :option:`replay_redirect`\= :file:`/dev/sdc` would cause all I/O
f80dba8d
MT
2324 in the blktrace or iolog to be replayed onto :file:`/dev/sdc`. This means
2325 multiple devices will be replayed onto a single device, if the trace
2326 contains multiple devices. If you want multiple devices to be replayed
2327 concurrently to multiple redirected devices you must blkparse your trace
2328 into separate traces and replay them with independent fio invocations.
2329 Unfortunately this also breaks the strict time ordering between multiple
2330 device accesses.
71bfa161 2331
f80dba8d 2332.. option:: replay_align=int
74929ac2 2333
f80dba8d
MT
2334 Force alignment of I/O offsets and lengths in a trace to this power of 2
2335 value.
3c54bc46 2336
f80dba8d 2337.. option:: replay_scale=int
3c54bc46 2338
f80dba8d 2339 Scale sector offsets down by this factor when replaying traces.
3c54bc46 2340
3c54bc46 2341
f80dba8d
MT
2342Threads, processes and job synchronization
2343~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
3c54bc46 2344
f80dba8d 2345.. option:: thread
3c54bc46 2346
730bd7d9
SW
2347 Fio defaults to creating jobs by using fork, however if this option is
2348 given, fio will create jobs by using POSIX Threads' function
2349 :manpage:`pthread_create(3)` to create threads instead.
71bfa161 2350
f80dba8d 2351.. option:: wait_for=str
74929ac2 2352
730bd7d9
SW
2353 If set, the current job won't be started until all workers of the specified
2354 waitee job are done.
74929ac2 2355
f80dba8d
MT
2356 ``wait_for`` operates on the job name basis, so there are a few
2357 limitations. First, the waitee must be defined prior to the waiter job
2358 (meaning no forward references). Second, if a job is being referenced as a
2359 waitee, it must have a unique name (no duplicate waitees).
74929ac2 2360
f80dba8d 2361.. option:: nice=int
892a6ffc 2362
f80dba8d 2363 Run the job with the given nice value. See man :manpage:`nice(2)`.
892a6ffc 2364
f80dba8d
MT
2365 On Windows, values less than -15 set the process class to "High"; -1 through
2366 -15 set "Above Normal"; 1 through 15 "Below Normal"; and above 15 "Idle"
2367 priority class.
74929ac2 2368
f80dba8d 2369.. option:: prio=int
71bfa161 2370
f80dba8d
MT
2371 Set the I/O priority value of this job. Linux limits us to a positive value
2372 between 0 and 7, with 0 being the highest. See man
2373 :manpage:`ionice(1)`. Refer to an appropriate manpage for other operating
2374 systems since meaning of priority may differ.
71bfa161 2375
f80dba8d 2376.. option:: prioclass=int
d59aa780 2377
f80dba8d 2378 Set the I/O priority class. See man :manpage:`ionice(1)`.
d59aa780 2379
f80dba8d 2380.. option:: cpus_allowed=str
6d500c2e 2381
730bd7d9 2382 Controls the same options as :option:`cpumask`, but accepts a textual
b570e037
SW
2383 specification of the permitted CPUs instead and CPUs are indexed from 0. So
2384 to use CPUs 0 and 5 you would specify ``cpus_allowed=0,5``. This option also
2385 allows a range of CPUs to be specified -- say you wanted a binding to CPUs
2386 0, 5, and 8 to 15, you would set ``cpus_allowed=0,5,8-15``.
2387
2388 On Windows, when ``cpus_allowed`` is unset only CPUs from fio's current
2389 processor group will be used and affinity settings are inherited from the
2390 system. An fio build configured to target Windows 7 makes options that set
2391 CPUs processor group aware and values will set both the processor group
2392 and a CPU from within that group. For example, on a system where processor
2393 group 0 has 40 CPUs and processor group 1 has 32 CPUs, ``cpus_allowed``
2394 values between 0 and 39 will bind CPUs from processor group 0 and
2395 ``cpus_allowed`` values between 40 and 71 will bind CPUs from processor
2396 group 1. When using ``cpus_allowed_policy=shared`` all CPUs specified by a
2397 single ``cpus_allowed`` option must be from the same processor group. For
2398 Windows fio builds not built for Windows 7, CPUs will only be selected from
2399 (and be relative to) whatever processor group fio happens to be running in
2400 and CPUs from other processor groups cannot be used.
6d500c2e 2401
f80dba8d 2402.. option:: cpus_allowed_policy=str
6d500c2e 2403
f80dba8d 2404 Set the policy of how fio distributes the CPUs specified by
730bd7d9 2405 :option:`cpus_allowed` or :option:`cpumask`. Two policies are supported:
6d500c2e 2406
f80dba8d
MT
2407 **shared**
2408 All jobs will share the CPU set specified.
2409 **split**
2410 Each job will get a unique CPU from the CPU set.
6d500c2e 2411
22413915 2412 **shared** is the default behavior, if the option isn't specified. If
f80dba8d
MT
2413 **split** is specified, then fio will will assign one cpu per job. If not
2414 enough CPUs are given for the jobs listed, then fio will roundrobin the CPUs
2415 in the set.
6d500c2e 2416
b570e037
SW
2417.. option:: cpumask=int
2418
2419 Set the CPU affinity of this job. The parameter given is a bit mask of
2420 allowed CPUs the job may run on. So if you want the allowed CPUs to be 1
2421 and 5, you would pass the decimal value of (1 << 1 | 1 << 5), or 34. See man
2422 :manpage:`sched_setaffinity(2)`. This may not work on all supported
2423 operating systems or kernel versions. This option doesn't work well for a
2424 higher CPU count than what you can store in an integer mask, so it can only
2425 control cpus 1-32. For boxes with larger CPU counts, use
2426 :option:`cpus_allowed`.
2427
f80dba8d 2428.. option:: numa_cpu_nodes=str
6d500c2e 2429
f80dba8d
MT
2430 Set this job running on specified NUMA nodes' CPUs. The arguments allow
2431 comma delimited list of cpu numbers, A-B ranges, or `all`. Note, to enable
ac8ca2af 2432 NUMA options support, fio must be built on a system with libnuma-dev(el)
f80dba8d 2433 installed.
61b9861d 2434
f80dba8d 2435.. option:: numa_mem_policy=str
61b9861d 2436
f80dba8d
MT
2437 Set this job's memory policy and corresponding NUMA nodes. Format of the
2438 arguments::
5c94b008 2439
f80dba8d 2440 <mode>[:<nodelist>]
ce35b1ec 2441
804c0839 2442 ``mode`` is one of the following memory policies: ``default``, ``prefer``,
730bd7d9
SW
2443 ``bind``, ``interleave`` or ``local``. For ``default`` and ``local`` memory
2444 policies, no node needs to be specified. For ``prefer``, only one node is
2445 allowed. For ``bind`` and ``interleave`` the ``nodelist`` may be as
2446 follows: a comma delimited list of numbers, A-B ranges, or `all`.
71bfa161 2447
f80dba8d 2448.. option:: cgroup=str
390b1537 2449
f80dba8d
MT
2450 Add job to this control group. If it doesn't exist, it will be created. The
2451 system must have a mounted cgroup blkio mount point for this to work. If
2452 your system doesn't have it mounted, you can do so with::
5af1c6f3 2453
f80dba8d 2454 # mount -t cgroup -o blkio none /cgroup
5af1c6f3 2455
f80dba8d 2456.. option:: cgroup_weight=int
5af1c6f3 2457
f80dba8d
MT
2458 Set the weight of the cgroup to this value. See the documentation that comes
2459 with the kernel, allowed values are in the range of 100..1000.
a086c257 2460
f80dba8d 2461.. option:: cgroup_nodelete=bool
8c07860d 2462
f80dba8d
MT
2463 Normally fio will delete the cgroups it has created after the job
2464 completion. To override this behavior and to leave cgroups around after the
2465 job completion, set ``cgroup_nodelete=1``. This can be useful if one wants
2466 to inspect various cgroup files after job completion. Default: false.
8c07860d 2467
f80dba8d 2468.. option:: flow_id=int
8c07860d 2469
f80dba8d
MT
2470 The ID of the flow. If not specified, it defaults to being a global
2471 flow. See :option:`flow`.
1907dbc6 2472
f80dba8d 2473.. option:: flow=int
71bfa161 2474
f80dba8d
MT
2475 Weight in token-based flow control. If this value is used, then there is a
2476 'flow counter' which is used to regulate the proportion of activity between
2477 two or more jobs. Fio attempts to keep this flow counter near zero. The
2478 ``flow`` parameter stands for how much should be added or subtracted to the
2479 flow counter on each iteration of the main I/O loop. That is, if one job has
2480 ``flow=8`` and another job has ``flow=-1``, then there will be a roughly 1:8
2481 ratio in how much one runs vs the other.
71bfa161 2482
f80dba8d 2483.. option:: flow_watermark=int
a31041ea 2484
f80dba8d
MT
2485 The maximum value that the absolute value of the flow counter is allowed to
2486 reach before the job must wait for a lower value of the counter.
82407585 2487
f80dba8d 2488.. option:: flow_sleep=int
82407585 2489
f80dba8d
MT
2490 The period of time, in microseconds, to wait after the flow watermark has
2491 been exceeded before retrying operations.
82407585 2492
f80dba8d 2493.. option:: stonewall, wait_for_previous
82407585 2494
f80dba8d
MT
2495 Wait for preceding jobs in the job file to exit, before starting this
2496 one. Can be used to insert serialization points in the job file. A stone
2497 wall also implies starting a new reporting group, see
2498 :option:`group_reporting`.
2499
2500.. option:: exitall
2501
730bd7d9
SW
2502 By default, fio will continue running all other jobs when one job finishes
2503 but sometimes this is not the desired action. Setting ``exitall`` will
2504 instead make fio terminate all other jobs when one job finishes.
f80dba8d
MT
2505
2506.. option:: exec_prerun=str
2507
2508 Before running this job, issue the command specified through
2509 :manpage:`system(3)`. Output is redirected in a file called
2510 :file:`jobname.prerun.txt`.
2511
2512.. option:: exec_postrun=str
2513
2514 After the job completes, issue the command specified though
2515 :manpage:`system(3)`. Output is redirected in a file called
2516 :file:`jobname.postrun.txt`.
2517
2518.. option:: uid=int
2519
2520 Instead of running as the invoking user, set the user ID to this value
2521 before the thread/process does any work.
2522
2523.. option:: gid=int
2524
2525 Set group ID, see :option:`uid`.
2526
2527
2528Verification
2529~~~~~~~~~~~~
2530
2531.. option:: verify_only
2532
2533 Do not perform specified workload, only verify data still matches previous
2534 invocation of this workload. This option allows one to check data multiple
2535 times at a later date without overwriting it. This option makes sense only
2536 for workloads that write data, and does not support workloads with the
2537 :option:`time_based` option set.
2538
2539.. option:: do_verify=bool
2540
2541 Run the verify phase after a write phase. Only valid if :option:`verify` is
2542 set. Default: true.
2543
2544.. option:: verify=str
2545
2546 If writing to a file, fio can verify the file contents after each iteration
2547 of the job. Each verification method also implies verification of special
2548 header, which is written to the beginning of each block. This header also
2549 includes meta information, like offset of the block, block number, timestamp
2550 when block was written, etc. :option:`verify` can be combined with
2551 :option:`verify_pattern` option. The allowed values are:
2552
2553 **md5**
2554 Use an md5 sum of the data area and store it in the header of
2555 each block.
2556
2557 **crc64**
2558 Use an experimental crc64 sum of the data area and store it in the
2559 header of each block.
2560
2561 **crc32c**
a5896300
SW
2562 Use a crc32c sum of the data area and store it in the header of
2563 each block. This will automatically use hardware acceleration
2564 (e.g. SSE4.2 on an x86 or CRC crypto extensions on ARM64) but will
2565 fall back to software crc32c if none is found. Generally the
804c0839 2566 fastest checksum fio supports when hardware accelerated.
f80dba8d
MT
2567
2568 **crc32c-intel**
a5896300 2569 Synonym for crc32c.
f80dba8d
MT
2570
2571 **crc32**
2572 Use a crc32 sum of the data area and store it in the header of each
2573 block.
2574
2575 **crc16**
2576 Use a crc16 sum of the data area and store it in the header of each
2577 block.
2578
2579 **crc7**
2580 Use a crc7 sum of the data area and store it in the header of each
2581 block.
2582
2583 **xxhash**
2584 Use xxhash as the checksum function. Generally the fastest software
2585 checksum that fio supports.
2586
2587 **sha512**
2588 Use sha512 as the checksum function.
2589
2590 **sha256**
2591 Use sha256 as the checksum function.
2592
2593 **sha1**
2594 Use optimized sha1 as the checksum function.
82407585 2595
ae3a5acc
JA
2596 **sha3-224**
2597 Use optimized sha3-224 as the checksum function.
2598
2599 **sha3-256**
2600 Use optimized sha3-256 as the checksum function.
2601
2602 **sha3-384**
2603 Use optimized sha3-384 as the checksum function.
2604
2605 **sha3-512**
2606 Use optimized sha3-512 as the checksum function.
2607
f80dba8d
MT
2608 **meta**
2609 This option is deprecated, since now meta information is included in
2610 generic verification header and meta verification happens by
2611 default. For detailed information see the description of the
2612 :option:`verify` setting. This option is kept because of
2613 compatibility's sake with old configurations. Do not use it.
2614
2615 **pattern**
2616 Verify a strict pattern. Normally fio includes a header with some
2617 basic information and checksumming, but if this option is set, only
2618 the specific pattern set with :option:`verify_pattern` is verified.
2619
2620 **null**
2621 Only pretend to verify. Useful for testing internals with
9207a0cb 2622 :option:`ioengine`\=null, not for much else.
f80dba8d
MT
2623
2624 This option can be used for repeated burn-in tests of a system to make sure
2625 that the written data is also correctly read back. If the data direction
2626 given is a read or random read, fio will assume that it should verify a
2627 previously written file. If the data direction includes any form of write,
2628 the verify will be of the newly written data.
2629
2630.. option:: verifysort=bool
2631
2632 If true, fio will sort written verify blocks when it deems it faster to read
2633 them back in a sorted manner. This is often the case when overwriting an
2634 existing file, since the blocks are already laid out in the file system. You
2635 can ignore this option unless doing huge amounts of really fast I/O where
2636 the red-black tree sorting CPU time becomes significant. Default: true.
2637
2638.. option:: verifysort_nr=int
2639
2b455dbf 2640 Pre-load and sort verify blocks for a read workload.
f80dba8d
MT
2641
2642.. option:: verify_offset=int
2643
2644 Swap the verification header with data somewhere else in the block before
2645 writing. It is swapped back before verifying.
2646
2647.. option:: verify_interval=int
2648
2649 Write the verification header at a finer granularity than the
2650 :option:`blocksize`. It will be written for chunks the size of
2651 ``verify_interval``. :option:`blocksize` should divide this evenly.
2652
2653.. option:: verify_pattern=str
2654
2655 If set, fio will fill the I/O buffers with this pattern. Fio defaults to
2656 filling with totally random bytes, but sometimes it's interesting to fill
2657 with a known pattern for I/O verification purposes. Depending on the width
730bd7d9 2658 of the pattern, fio will fill 1/2/3/4 bytes of the buffer at the time (it can
f80dba8d
MT
2659 be either a decimal or a hex number). The ``verify_pattern`` if larger than
2660 a 32-bit quantity has to be a hex number that starts with either "0x" or
2661 "0X". Use with :option:`verify`. Also, ``verify_pattern`` supports %o
2662 format, which means that for each block offset will be written and then
2663 verified back, e.g.::
61b9861d
RP
2664
2665 verify_pattern=%o
2666
f80dba8d
MT
2667 Or use combination of everything::
2668
61b9861d 2669 verify_pattern=0xff%o"abcd"-12
e28218f3 2670
f80dba8d
MT
2671.. option:: verify_fatal=bool
2672
2673 Normally fio will keep checking the entire contents before quitting on a
2674 block verification failure. If this option is set, fio will exit the job on
2675 the first observed failure. Default: false.
2676
2677.. option:: verify_dump=bool
2678
2679 If set, dump the contents of both the original data block and the data block
2680 we read off disk to files. This allows later analysis to inspect just what
2681 kind of data corruption occurred. Off by default.
2682
2683.. option:: verify_async=int
2684
2685 Fio will normally verify I/O inline from the submitting thread. This option
2686 takes an integer describing how many async offload threads to create for I/O
2687 verification instead, causing fio to offload the duty of verifying I/O
2688 contents to one or more separate threads. If using this offload option, even
2689 sync I/O engines can benefit from using an :option:`iodepth` setting higher
2690 than 1, as it allows them to have I/O in flight while verifies are running.
d7e6ea1c 2691 Defaults to 0 async threads, i.e. verification is not asynchronous.
f80dba8d
MT
2692
2693.. option:: verify_async_cpus=str
2694
2695 Tell fio to set the given CPU affinity on the async I/O verification
2696 threads. See :option:`cpus_allowed` for the format used.
2697
2698.. option:: verify_backlog=int
2699
2700 Fio will normally verify the written contents of a job that utilizes verify
2701 once that job has completed. In other words, everything is written then
2702 everything is read back and verified. You may want to verify continually
2703 instead for a variety of reasons. Fio stores the meta data associated with
2704 an I/O block in memory, so for large verify workloads, quite a bit of memory
2705 would be used up holding this meta data. If this option is enabled, fio will
2706 write only N blocks before verifying these blocks.
2707
2708.. option:: verify_backlog_batch=int
2709
2710 Control how many blocks fio will verify if :option:`verify_backlog` is
2711 set. If not set, will default to the value of :option:`verify_backlog`
2712 (meaning the entire queue is read back and verified). If
2713 ``verify_backlog_batch`` is less than :option:`verify_backlog` then not all
2714 blocks will be verified, if ``verify_backlog_batch`` is larger than
2715 :option:`verify_backlog`, some blocks will be verified more than once.
2716
2717.. option:: verify_state_save=bool
2718
2719 When a job exits during the write phase of a verify workload, save its
2720 current state. This allows fio to replay up until that point, if the verify
2721 state is loaded for the verify read phase. The format of the filename is,
2722 roughly::
2723
f50fbdda 2724 <type>-<jobname>-<jobindex>-verify.state.
f80dba8d
MT
2725
2726 <type> is "local" for a local run, "sock" for a client/server socket
2727 connection, and "ip" (192.168.0.1, for instance) for a networked
d7e6ea1c 2728 client/server connection. Defaults to true.
f80dba8d
MT
2729
2730.. option:: verify_state_load=bool
2731
2732 If a verify termination trigger was used, fio stores the current write state
2733 of each thread. This can be used at verification time so that fio knows how
2734 far it should verify. Without this information, fio will run a full
a47b697c
SW
2735 verification pass, according to the settings in the job file used. Default
2736 false.
f80dba8d
MT
2737
2738.. option:: trim_percentage=int
2739
2740 Number of verify blocks to discard/trim.
2741
2742.. option:: trim_verify_zero=bool
2743
22413915 2744 Verify that trim/discarded blocks are returned as zeros.
f80dba8d
MT
2745
2746.. option:: trim_backlog=int
2747
5cfd1e9a 2748 Trim after this number of blocks are written.
f80dba8d
MT
2749
2750.. option:: trim_backlog_batch=int
2751
2752 Trim this number of I/O blocks.
2753
2754.. option:: experimental_verify=bool
2755
2756 Enable experimental verification.
2757
f80dba8d
MT
2758Steady state
2759~~~~~~~~~~~~
2760
2761.. option:: steadystate=str:float, ss=str:float
2762
2763 Define the criterion and limit for assessing steady state performance. The
2764 first parameter designates the criterion whereas the second parameter sets
2765 the threshold. When the criterion falls below the threshold for the
2766 specified duration, the job will stop. For example, `iops_slope:0.1%` will
2767 direct fio to terminate the job when the least squares regression slope
2768 falls below 0.1% of the mean IOPS. If :option:`group_reporting` is enabled
2769 this will apply to all jobs in the group. Below is the list of available
2770 steady state assessment criteria. All assessments are carried out using only
2771 data from the rolling collection window. Threshold limits can be expressed
2772 as a fixed value or as a percentage of the mean in the collection window.
2773
2774 **iops**
2775 Collect IOPS data. Stop the job if all individual IOPS measurements
2776 are within the specified limit of the mean IOPS (e.g., ``iops:2``
2777 means that all individual IOPS values must be within 2 of the mean,
2778 whereas ``iops:0.2%`` means that all individual IOPS values must be
2779 within 0.2% of the mean IOPS to terminate the job).
2780
2781 **iops_slope**
2782 Collect IOPS data and calculate the least squares regression
2783 slope. Stop the job if the slope falls below the specified limit.
2784
2785 **bw**
2786 Collect bandwidth data. Stop the job if all individual bandwidth
2787 measurements are within the specified limit of the mean bandwidth.
2788
2789 **bw_slope**
2790 Collect bandwidth data and calculate the least squares regression
2791 slope. Stop the job if the slope falls below the specified limit.
2792
2793.. option:: steadystate_duration=time, ss_dur=time
2794
2795 A rolling window of this duration will be used to judge whether steady state
2796 has been reached. Data will be collected once per second. The default is 0
f75ede1d 2797 which disables steady state detection. When the unit is omitted, the
947e0fe0 2798 value is interpreted in seconds.
f80dba8d
MT
2799
2800.. option:: steadystate_ramp_time=time, ss_ramp=time
2801
2802 Allow the job to run for the specified duration before beginning data
2803 collection for checking the steady state job termination criterion. The
947e0fe0 2804 default is 0. When the unit is omitted, the value is interpreted in seconds.
f80dba8d
MT
2805
2806
2807Measurements and reporting
2808~~~~~~~~~~~~~~~~~~~~~~~~~~
2809
2810.. option:: per_job_logs=bool
2811
2812 If set, this generates bw/clat/iops log with per file private filenames. If
2813 not set, jobs with identical names will share the log filename. Default:
2814 true.
2815
2816.. option:: group_reporting
2817
2818 It may sometimes be interesting to display statistics for groups of jobs as
2819 a whole instead of for each individual job. This is especially true if
2820 :option:`numjobs` is used; looking at individual thread/process output
2821 quickly becomes unwieldy. To see the final report per-group instead of
2822 per-job, use :option:`group_reporting`. Jobs in a file will be part of the
2823 same reporting group, unless if separated by a :option:`stonewall`, or by
2824 using :option:`new_group`.
2825
2826.. option:: new_group
2827
2828 Start a new reporting group. See: :option:`group_reporting`. If not given,
2829 all jobs in a file will be part of the same reporting group, unless
2830 separated by a :option:`stonewall`.
2831
589e88b7 2832.. option:: stats=bool
8243be59
JA
2833
2834 By default, fio collects and shows final output results for all jobs
2835 that run. If this option is set to 0, then fio will ignore it in
2836 the final stat output.
2837
f80dba8d
MT
2838.. option:: write_bw_log=str
2839
2840 If given, write a bandwidth log for this job. Can be used to store data of
074f0817 2841 the bandwidth of the jobs in their lifetime.
f80dba8d 2842
074f0817
SW
2843 If no str argument is given, the default filename of
2844 :file:`jobname_type.x.log` is used. Even when the argument is given, fio
2845 will still append the type of log. So if one specifies::
2846
2847 write_bw_log=foo
f80dba8d 2848
074f0817
SW
2849 The actual log name will be :file:`foo_bw.x.log` where `x` is the index
2850 of the job (`1..N`, where `N` is the number of jobs). If
2851 :option:`per_job_logs` is false, then the filename will not include the
2852 `.x` job index.
e3cedca7 2853
074f0817
SW
2854 The included :command:`fio_generate_plots` script uses :command:`gnuplot` to turn these
2855 text files into nice graphs. See `Log File Formats`_ for how data is
2856 structured within the file.
2857
2858.. option:: write_lat_log=str
e3cedca7 2859
074f0817 2860 Same as :option:`write_bw_log`, except this option creates I/O
77b7e675
SW
2861 submission (e.g., :file:`name_slat.x.log`), completion (e.g.,
2862 :file:`name_clat.x.log`), and total (e.g., :file:`name_lat.x.log`)
074f0817
SW
2863 latency files instead. See :option:`write_bw_log` for details about
2864 the filename format and `Log File Formats`_ for how data is structured
2865 within the files.
be4ecfdf 2866
f80dba8d 2867.. option:: write_hist_log=str
06842027 2868
074f0817 2869 Same as :option:`write_bw_log` but writes an I/O completion latency
77b7e675 2870 histogram file (e.g., :file:`name_hist.x.log`) instead. Note that this
074f0817
SW
2871 file will be empty unless :option:`log_hist_msec` has also been set.
2872 See :option:`write_bw_log` for details about the filename format and
2873 `Log File Formats`_ for how data is structured within the file.
06842027 2874
f80dba8d 2875.. option:: write_iops_log=str
06842027 2876
074f0817 2877 Same as :option:`write_bw_log`, but writes an IOPS file (e.g.
77b7e675 2878 :file:`name_iops.x.log`) instead. See :option:`write_bw_log` for
074f0817
SW
2879 details about the filename format and `Log File Formats`_ for how data
2880 is structured within the file.
06842027 2881
f80dba8d 2882.. option:: log_avg_msec=int
06842027 2883
f80dba8d
MT
2884 By default, fio will log an entry in the iops, latency, or bw log for every
2885 I/O that completes. When writing to the disk log, that can quickly grow to a
2886 very large size. Setting this option makes fio average the each log entry
2887 over the specified period of time, reducing the resolution of the log. See
2888 :option:`log_max_value` as well. Defaults to 0, logging all entries.
6fc82095 2889 Also see `Log File Formats`_.
06842027 2890
f80dba8d 2891.. option:: log_hist_msec=int
06842027 2892
f80dba8d
MT
2893 Same as :option:`log_avg_msec`, but logs entries for completion latency
2894 histograms. Computing latency percentiles from averages of intervals using
c60ebc45 2895 :option:`log_avg_msec` is inaccurate. Setting this option makes fio log
f80dba8d
MT
2896 histogram entries over the specified period of time, reducing log sizes for
2897 high IOPS devices while retaining percentile accuracy. See
074f0817
SW
2898 :option:`log_hist_coarseness` and :option:`write_hist_log` as well.
2899 Defaults to 0, meaning histogram logging is disabled.
06842027 2900
f80dba8d 2901.. option:: log_hist_coarseness=int
06842027 2902
f80dba8d
MT
2903 Integer ranging from 0 to 6, defining the coarseness of the resolution of
2904 the histogram logs enabled with :option:`log_hist_msec`. For each increment
2905 in coarseness, fio outputs half as many bins. Defaults to 0, for which
074f0817
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2906 histogram logs contain 1216 latency bins. See :option:`write_hist_log`
2907 and `Log File Formats`_.
8b28bd41 2908
f80dba8d 2909.. option:: log_max_value=bool
66c098b8 2910
f80dba8d
MT
2911 If :option:`log_avg_msec` is set, fio logs the average over that window. If
2912 you instead want to log the maximum value, set this option to 1. Defaults to
2913 0, meaning that averaged values are logged.
a696fa2a 2914
589e88b7 2915.. option:: log_offset=bool
a696fa2a 2916
f80dba8d 2917 If this is set, the iolog options will include the byte offset for the I/O
5a83478f
SW
2918 entry as well as the other data values. Defaults to 0 meaning that
2919 offsets are not present in logs. Also see `Log File Formats`_.
71bfa161 2920
f80dba8d 2921.. option:: log_compression=int
7de87099 2922
f80dba8d
MT
2923 If this is set, fio will compress the I/O logs as it goes, to keep the
2924 memory footprint lower. When a log reaches the specified size, that chunk is
2925 removed and compressed in the background. Given that I/O logs are fairly
2926 highly compressible, this yields a nice memory savings for longer runs. The
2927 downside is that the compression will consume some background CPU cycles, so
2928 it may impact the run. This, however, is also true if the logging ends up
2929 consuming most of the system memory. So pick your poison. The I/O logs are
2930 saved normally at the end of a run, by decompressing the chunks and storing
2931 them in the specified log file. This feature depends on the availability of
2932 zlib.
e0b0d892 2933
f80dba8d 2934.. option:: log_compression_cpus=str
e0b0d892 2935
f80dba8d
MT
2936 Define the set of CPUs that are allowed to handle online log compression for
2937 the I/O jobs. This can provide better isolation between performance
0cf90a62
SW
2938 sensitive jobs, and background compression work. See
2939 :option:`cpus_allowed` for the format used.
9e684a49 2940
f80dba8d 2941.. option:: log_store_compressed=bool
9e684a49 2942
f80dba8d
MT
2943 If set, fio will store the log files in a compressed format. They can be
2944 decompressed with fio, using the :option:`--inflate-log` command line
2945 parameter. The files will be stored with a :file:`.fz` suffix.
9e684a49 2946
f80dba8d 2947.. option:: log_unix_epoch=bool
9e684a49 2948
f80dba8d
MT
2949 If set, fio will log Unix timestamps to the log files produced by enabling
2950 write_type_log for each log type, instead of the default zero-based
2951 timestamps.
2952
2953.. option:: block_error_percentiles=bool
2954
2955 If set, record errors in trim block-sized units from writes and trims and
2956 output a histogram of how many trims it took to get to errors, and what kind
2957 of error was encountered.
2958
2959.. option:: bwavgtime=int
2960
2961 Average the calculated bandwidth over the given time. Value is specified in
2962 milliseconds. If the job also does bandwidth logging through
2963 :option:`write_bw_log`, then the minimum of this option and
2964 :option:`log_avg_msec` will be used. Default: 500ms.
2965
2966.. option:: iopsavgtime=int
2967
2968 Average the calculated IOPS over the given time. Value is specified in
2969 milliseconds. If the job also does IOPS logging through
2970 :option:`write_iops_log`, then the minimum of this option and
2971 :option:`log_avg_msec` will be used. Default: 500ms.
2972
2973.. option:: disk_util=bool
2974
2975 Generate disk utilization statistics, if the platform supports it.
2976 Default: true.
2977
2978.. option:: disable_lat=bool
2979
2980 Disable measurements of total latency numbers. Useful only for cutting back
2981 the number of calls to :manpage:`gettimeofday(2)`, as that does impact
2982 performance at really high IOPS rates. Note that to really get rid of a
2983 large amount of these calls, this option must be used with
f75ede1d 2984 :option:`disable_slat` and :option:`disable_bw_measurement` as well.
f80dba8d
MT
2985
2986.. option:: disable_clat=bool
2987
2988 Disable measurements of completion latency numbers. See
2989 :option:`disable_lat`.
2990
2991.. option:: disable_slat=bool
2992
2993 Disable measurements of submission latency numbers. See
f50fbdda 2994 :option:`disable_lat`.
f80dba8d 2995
f75ede1d 2996.. option:: disable_bw_measurement=bool, disable_bw=bool
f80dba8d
MT
2997
2998 Disable measurements of throughput/bandwidth numbers. See
2999 :option:`disable_lat`.
3000
3001.. option:: clat_percentiles=bool
3002
b599759b
JA
3003 Enable the reporting of percentiles of completion latencies. This
3004 option is mutually exclusive with :option:`lat_percentiles`.
3005
3006.. option:: lat_percentiles=bool
3007
b71968b1 3008 Enable the reporting of percentiles of I/O latencies. This is similar
b599759b
JA
3009 to :option:`clat_percentiles`, except that this includes the
3010 submission latency. This option is mutually exclusive with
3011 :option:`clat_percentiles`.
f80dba8d
MT
3012
3013.. option:: percentile_list=float_list
3014
c32ba107
JA
3015 Overwrite the default list of percentiles for completion latencies and
3016 the block error histogram. Each number is a floating number in the
3017 range (0,100], and the maximum length of the list is 20. Use ``:`` to
3018 separate the numbers, and list the numbers in ascending order. For
3019 example, ``--percentile_list=99.5:99.9`` will cause fio to report the
3020 values of completion latency below which 99.5% and 99.9% of the observed
3021 latencies fell, respectively.
f80dba8d 3022
e883cb35
JF
3023.. option:: significant_figures=int
3024
c32ba107
JA
3025 If using :option:`--output-format` of `normal`, set the significant
3026 figures to this value. Higher values will yield more precise IOPS and
3027 throughput units, while lower values will round. Requires a minimum
3028 value of 1 and a maximum value of 10. Defaults to 4.
e883cb35 3029
f80dba8d
MT
3030
3031Error handling
3032~~~~~~~~~~~~~~
3033
3034.. option:: exitall_on_error
3035
3036 When one job finishes in error, terminate the rest. The default is to wait
3037 for each job to finish.
3038
3039.. option:: continue_on_error=str
3040
3041 Normally fio will exit the job on the first observed failure. If this option
3042 is set, fio will continue the job when there is a 'non-fatal error' (EIO or
3043 EILSEQ) until the runtime is exceeded or the I/O size specified is
3044 completed. If this option is used, there are two more stats that are
3045 appended, the total error count and the first error. The error field given
3046 in the stats is the first error that was hit during the run.
3047
3048 The allowed values are:
3049
3050 **none**
3051 Exit on any I/O or verify errors.
3052
3053 **read**
3054 Continue on read errors, exit on all others.
3055
3056 **write**
3057 Continue on write errors, exit on all others.
3058
3059 **io**
3060 Continue on any I/O error, exit on all others.
3061
3062 **verify**
3063 Continue on verify errors, exit on all others.
3064
3065 **all**
3066 Continue on all errors.
3067
3068 **0**
3069 Backward-compatible alias for 'none'.
3070
3071 **1**
3072 Backward-compatible alias for 'all'.
3073
3074.. option:: ignore_error=str
3075
3076 Sometimes you want to ignore some errors during test in that case you can
a35ef7cb
TK
3077 specify error list for each error type, instead of only being able to
3078 ignore the default 'non-fatal error' using :option:`continue_on_error`.
f80dba8d
MT
3079 ``ignore_error=READ_ERR_LIST,WRITE_ERR_LIST,VERIFY_ERR_LIST`` errors for
3080 given error type is separated with ':'. Error may be symbol ('ENOSPC',
3081 'ENOMEM') or integer. Example::
3082
3083 ignore_error=EAGAIN,ENOSPC:122
3084
3085 This option will ignore EAGAIN from READ, and ENOSPC and 122(EDQUOT) from
a35ef7cb
TK
3086 WRITE. This option works by overriding :option:`continue_on_error` with
3087 the list of errors for each error type if any.
f80dba8d
MT
3088
3089.. option:: error_dump=bool
3090
3091 If set dump every error even if it is non fatal, true by default. If
3092 disabled only fatal error will be dumped.
3093
f75ede1d
SW
3094Running predefined workloads
3095----------------------------
3096
3097Fio includes predefined profiles that mimic the I/O workloads generated by
3098other tools.
3099
3100.. option:: profile=str
3101
3102 The predefined workload to run. Current profiles are:
3103
3104 **tiobench**
3105 Threaded I/O bench (tiotest/tiobench) like workload.
3106
3107 **act**
3108 Aerospike Certification Tool (ACT) like workload.
3109
3110To view a profile's additional options use :option:`--cmdhelp` after specifying
3111the profile. For example::
3112
f50fbdda 3113 $ fio --profile=act --cmdhelp
f75ede1d
SW
3114
3115Act profile options
3116~~~~~~~~~~~~~~~~~~~
3117
3118.. option:: device-names=str
3119 :noindex:
3120
3121 Devices to use.
3122
3123.. option:: load=int
3124 :noindex:
3125
3126 ACT load multiplier. Default: 1.
3127
3128.. option:: test-duration=time
3129 :noindex:
3130
947e0fe0
SW
3131 How long the entire test takes to run. When the unit is omitted, the value
3132 is given in seconds. Default: 24h.
f75ede1d
SW
3133
3134.. option:: threads-per-queue=int
3135 :noindex:
3136
f50fbdda 3137 Number of read I/O threads per device. Default: 8.
f75ede1d
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3138
3139.. option:: read-req-num-512-blocks=int
3140 :noindex:
3141
3142 Number of 512B blocks to read at the time. Default: 3.
3143
3144.. option:: large-block-op-kbytes=int
3145 :noindex:
3146
3147 Size of large block ops in KiB (writes). Default: 131072.
3148
3149.. option:: prep
3150 :noindex:
3151
3152 Set to run ACT prep phase.
3153
3154Tiobench profile options
3155~~~~~~~~~~~~~~~~~~~~~~~~
3156
3157.. option:: size=str
3158 :noindex:
3159
f50fbdda 3160 Size in MiB.
f75ede1d
SW
3161
3162.. option:: block=int
3163 :noindex:
3164
3165 Block size in bytes. Default: 4096.
3166
3167.. option:: numruns=int
3168 :noindex:
3169
3170 Number of runs.
3171
3172.. option:: dir=str
3173 :noindex:
3174
3175 Test directory.
3176
3177.. option:: threads=int
3178 :noindex:
3179
3180 Number of threads.
f80dba8d
MT
3181
3182Interpreting the output
3183-----------------------
3184
36214730
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3185..
3186 Example output was based on the following:
3187 TZ=UTC fio --iodepth=8 --ioengine=null --size=100M --time_based \
3188 --rate=1256k --bs=14K --name=quick --runtime=1s --name=mixed \
3189 --runtime=2m --rw=rw
3190
f80dba8d
MT
3191Fio spits out a lot of output. While running, fio will display the status of the
3192jobs created. An example of that would be::
3193
9d25d068 3194 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]
f80dba8d 3195
36214730
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3196The characters inside the first set of square brackets denote the current status of
3197each thread. The first character is the first job defined in the job file, and so
3198forth. The possible values (in typical life cycle order) are:
f80dba8d
MT
3199
3200+------+-----+-----------------------------------------------------------+
3201| Idle | Run | |
3202+======+=====+===========================================================+
3203| P | | Thread setup, but not started. |
3204+------+-----+-----------------------------------------------------------+
3205| C | | Thread created. |
3206+------+-----+-----------------------------------------------------------+
3207| I | | Thread initialized, waiting or generating necessary data. |
3208+------+-----+-----------------------------------------------------------+
3209| | p | Thread running pre-reading file(s). |
3210+------+-----+-----------------------------------------------------------+
36214730
SW
3211| | / | Thread is in ramp period. |
3212+------+-----+-----------------------------------------------------------+
f80dba8d
MT
3213| | R | Running, doing sequential reads. |
3214+------+-----+-----------------------------------------------------------+
3215| | r | Running, doing random reads. |
3216+------+-----+-----------------------------------------------------------+
3217| | W | Running, doing sequential writes. |
3218+------+-----+-----------------------------------------------------------+
3219| | w | Running, doing random writes. |
3220+------+-----+-----------------------------------------------------------+
3221| | M | Running, doing mixed sequential reads/writes. |
3222+------+-----+-----------------------------------------------------------+
3223| | m | Running, doing mixed random reads/writes. |
3224+------+-----+-----------------------------------------------------------+
36214730
SW
3225| | D | Running, doing sequential trims. |
3226+------+-----+-----------------------------------------------------------+
3227| | d | Running, doing random trims. |
3228+------+-----+-----------------------------------------------------------+
3229| | F | Running, currently waiting for :manpage:`fsync(2)`. |
f80dba8d
MT
3230+------+-----+-----------------------------------------------------------+
3231| | V | Running, doing verification of written data. |
3232+------+-----+-----------------------------------------------------------+
36214730
SW
3233| f | | Thread finishing. |
3234+------+-----+-----------------------------------------------------------+
f80dba8d
MT
3235| E | | Thread exited, not reaped by main thread yet. |
3236+------+-----+-----------------------------------------------------------+
36214730 3237| _ | | Thread reaped. |
f80dba8d
MT
3238+------+-----+-----------------------------------------------------------+
3239| X | | Thread reaped, exited with an error. |
3240+------+-----+-----------------------------------------------------------+
3241| K | | Thread reaped, exited due to signal. |
3242+------+-----+-----------------------------------------------------------+
3243
36214730
SW
3244..
3245 Example output was based on the following:
3246 TZ=UTC fio --iodepth=8 --ioengine=null --size=100M --runtime=58m \
3247 --time_based --rate=2512k --bs=256K --numjobs=10 \
3248 --name=readers --rw=read --name=writers --rw=write
3249
f80dba8d 3250Fio will condense the thread string as not to take up more space on the command
36214730 3251line than needed. For instance, if you have 10 readers and 10 writers running,
f80dba8d
MT
3252the output would look like this::
3253
9d25d068 3254 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]
f80dba8d 3255
36214730
SW
3256Note that the status string is displayed in order, so it's possible to tell which of
3257the jobs are currently doing what. In the example above this means that jobs 1--10
3258are readers and 11--20 are writers.
f80dba8d
MT
3259
3260The other values are fairly self explanatory -- number of threads currently
36214730
SW
3261running and doing I/O, the number of currently open files (f=), the estimated
3262completion percentage, the rate of I/O since last check (read speed listed first,
f50fbdda
TK
3263then write speed and optionally trim speed) in terms of bandwidth and IOPS,
3264and time to completion for the current running group. It's impossible to estimate
3265runtime of the following groups (if any).
36214730
SW
3266
3267..
3268 Example output was based on the following:
3269 TZ=UTC fio --iodepth=16 --ioengine=posixaio --filename=/tmp/fiofile \
3270 --direct=1 --size=100M --time_based --runtime=50s --rate_iops=89 \
3271 --bs=7K --name=Client1 --rw=write
3272
3273When fio is done (or interrupted by :kbd:`Ctrl-C`), it will show the data for
3274each thread, group of threads, and disks in that order. For each overall thread (or
3275group) the output looks like::
3276
3277 Client1: (groupid=0, jobs=1): err= 0: pid=16109: Sat Jun 24 12:07:54 2017
3278 write: IOPS=88, BW=623KiB/s (638kB/s)(30.4MiB/50032msec)
3279 slat (nsec): min=500, max=145500, avg=8318.00, stdev=4781.50
3280 clat (usec): min=170, max=78367, avg=4019.02, stdev=8293.31
3281 lat (usec): min=174, max=78375, avg=4027.34, stdev=8291.79
3282 clat percentiles (usec):
3283 | 1.00th=[ 302], 5.00th=[ 326], 10.00th=[ 343], 20.00th=[ 363],
3284 | 30.00th=[ 392], 40.00th=[ 404], 50.00th=[ 416], 60.00th=[ 445],
3285 | 70.00th=[ 816], 80.00th=[ 6718], 90.00th=[12911], 95.00th=[21627],
3286 | 99.00th=[43779], 99.50th=[51643], 99.90th=[68682], 99.95th=[72877],
3287 | 99.99th=[78119]
3288 bw ( KiB/s): min= 532, max= 686, per=0.10%, avg=622.87, stdev=24.82, samples= 100
3289 iops : min= 76, max= 98, avg=88.98, stdev= 3.54, samples= 100
29092211
VF
3290 lat (usec) : 250=0.04%, 500=64.11%, 750=4.81%, 1000=2.79%
3291 lat (msec) : 2=4.16%, 4=1.84%, 10=4.90%, 20=11.33%, 50=5.37%
3292 lat (msec) : 100=0.65%
36214730
SW
3293 cpu : usr=0.27%, sys=0.18%, ctx=12072, majf=0, minf=21
3294 IO depths : 1=85.0%, 2=13.1%, 4=1.8%, 8=0.1%, 16=0.0%, 32=0.0%, >=64=0.0%
3295 submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
3296 complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
3297 issued rwt: total=0,4450,0, short=0,0,0, dropped=0,0,0
3298 latency : target=0, window=0, percentile=100.00%, depth=8
3299
3300The job name (or first job's name when using :option:`group_reporting`) is printed,
3301along with the group id, count of jobs being aggregated, last error id seen (which
3302is 0 when there are no errors), pid/tid of that thread and the time the job/group
3303completed. Below are the I/O statistics for each data direction performed (showing
3304writes in the example above). In the order listed, they denote:
3305
3306**read/write/trim**
3307 The string before the colon shows the I/O direction the statistics
3308 are for. **IOPS** is the average I/Os performed per second. **BW**
3309 is the average bandwidth rate shown as: value in power of 2 format
3310 (value in power of 10 format). The last two values show: (**total
3311 I/O performed** in power of 2 format / **runtime** of that thread).
f80dba8d
MT
3312
3313**slat**
36214730
SW
3314 Submission latency (**min** being the minimum, **max** being the
3315 maximum, **avg** being the average, **stdev** being the standard
3316 deviation). This is the time it took to submit the I/O. For
3317 sync I/O this row is not displayed as the slat is really the
3318 completion latency (since queue/complete is one operation there).
3319 This value can be in nanoseconds, microseconds or milliseconds ---
3320 fio will choose the most appropriate base and print that (in the
3321 example above nanoseconds was the best scale). Note: in :option:`--minimal` mode
0d237712 3322 latencies are always expressed in microseconds.
f80dba8d
MT
3323
3324**clat**
3325 Completion latency. Same names as slat, this denotes the time from
3326 submission to completion of the I/O pieces. For sync I/O, clat will
3327 usually be equal (or very close) to 0, as the time from submit to
3328 complete is basically just CPU time (I/O has already been done, see slat
3329 explanation).
3330
29092211
VF
3331**lat**
3332 Total latency. Same names as slat and clat, this denotes the time from
3333 when fio created the I/O unit to completion of the I/O operation.
3334
f80dba8d 3335**bw**
36214730
SW
3336 Bandwidth statistics based on samples. Same names as the xlat stats,
3337 but also includes the number of samples taken (**samples**) and an
3338 approximate percentage of total aggregate bandwidth this thread
3339 received in its group (**per**). This last value is only really
3340 useful if the threads in this group are on the same disk, since they
3341 are then competing for disk access.
3342
3343**iops**
3344 IOPS statistics based on samples. Same names as bw.
f80dba8d 3345
29092211
VF
3346**lat (nsec/usec/msec)**
3347 The distribution of I/O completion latencies. This is the time from when
3348 I/O leaves fio and when it gets completed. Unlike the separate
3349 read/write/trim sections above, the data here and in the remaining
3350 sections apply to all I/Os for the reporting group. 250=0.04% means that
3351 0.04% of the I/Os completed in under 250us. 500=64.11% means that 64.11%
3352 of the I/Os required 250 to 499us for completion.
3353
f80dba8d
MT
3354**cpu**
3355 CPU usage. User and system time, along with the number of context
3356 switches this thread went through, usage of system and user time, and
3357 finally the number of major and minor page faults. The CPU utilization
3358 numbers are averages for the jobs in that reporting group, while the
23a8e176 3359 context and fault counters are summed.
f80dba8d
MT
3360
3361**IO depths**
a2140525
SW
3362 The distribution of I/O depths over the job lifetime. The numbers are
3363 divided into powers of 2 and each entry covers depths from that value
3364 up to those that are lower than the next entry -- e.g., 16= covers
3365 depths from 16 to 31. Note that the range covered by a depth
3366 distribution entry can be different to the range covered by the
3367 equivalent submit/complete distribution entry.
f80dba8d
MT
3368
3369**IO submit**
3370 How many pieces of I/O were submitting in a single submit call. Each
c60ebc45 3371 entry denotes that amount and below, until the previous entry -- e.g.,
a2140525
SW
3372 16=100% means that we submitted anywhere between 9 to 16 I/Os per submit
3373 call. Note that the range covered by a submit distribution entry can
3374 be different to the range covered by the equivalent depth distribution
3375 entry.
f80dba8d
MT
3376
3377**IO complete**
3378 Like the above submit number, but for completions instead.
3379
36214730
SW
3380**IO issued rwt**
3381 The number of read/write/trim requests issued, and how many of them were
3382 short or dropped.
f80dba8d 3383
29092211 3384**IO latency**
ee21ebee 3385 These values are for :option:`latency_target` and related options. When
29092211
VF
3386 these options are engaged, this section describes the I/O depth required
3387 to meet the specified latency target.
71bfa161 3388
36214730
SW
3389..
3390 Example output was based on the following:
3391 TZ=UTC fio --ioengine=null --iodepth=2 --size=100M --numjobs=2 \
3392 --rate_process=poisson --io_limit=32M --name=read --bs=128k \
3393 --rate=11M --name=write --rw=write --bs=2k --rate=700k
3394
71bfa161 3395After each client has been listed, the group statistics are printed. They
f80dba8d 3396will look like this::
71bfa161 3397
f80dba8d 3398 Run status group 0 (all jobs):
36214730
SW
3399 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
3400 WRITE: bw=1231KiB/s (1261kB/s), 616KiB/s-621KiB/s (630kB/s-636kB/s), io=64.0MiB (67.1MB), run=52747-53223msec
71bfa161 3401
36214730 3402For each data direction it prints:
71bfa161 3403
36214730
SW
3404**bw**
3405 Aggregate bandwidth of threads in this group followed by the
3406 minimum and maximum bandwidth of all the threads in this group.
3407 Values outside of brackets are power-of-2 format and those
3408 within are the equivalent value in a power-of-10 format.
f80dba8d 3409**io**
36214730
SW
3410 Aggregate I/O performed of all threads in this group. The
3411 format is the same as bw.
3412**run**
3413 The smallest and longest runtimes of the threads in this group.
71bfa161 3414
f50fbdda 3415And finally, the disk statistics are printed. This is Linux specific. They will look like this::
71bfa161 3416
f80dba8d
MT
3417 Disk stats (read/write):
3418 sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00%
71bfa161
JA
3419
3420Each value is printed for both reads and writes, with reads first. The
3421numbers denote:
3422
f80dba8d 3423**ios**
c60ebc45 3424 Number of I/Os performed by all groups.
f80dba8d 3425**merge**
007c7be9 3426 Number of merges performed by the I/O scheduler.
f80dba8d
MT
3427**ticks**
3428 Number of ticks we kept the disk busy.
36214730 3429**in_queue**
f80dba8d
MT
3430 Total time spent in the disk queue.
3431**util**
3432 The disk utilization. A value of 100% means we kept the disk
71bfa161
JA
3433 busy constantly, 50% would be a disk idling half of the time.
3434
f80dba8d
MT
3435It is also possible to get fio to dump the current output while it is running,
3436without terminating the job. To do that, send fio the **USR1** signal. You can
3437also get regularly timed dumps by using the :option:`--status-interval`
3438parameter, or by creating a file in :file:`/tmp` named
3439:file:`fio-dump-status`. If fio sees this file, it will unlink it and dump the
3440current output status.
8423bd11 3441
71bfa161 3442
f80dba8d
MT
3443Terse output
3444------------
71bfa161 3445
f80dba8d
MT
3446For scripted usage where you typically want to generate tables or graphs of the
3447results, fio can output the results in a semicolon separated format. The format
3448is one long line of values, such as::
71bfa161 3449
f80dba8d
MT
3450 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%
3451 A description of this job goes here.
562c2d2f
DN
3452
3453The job description (if provided) follows on a second line.
71bfa161 3454
a7f77fa6
SW
3455To enable terse output, use the :option:`--minimal` or
3456:option:`--output-format`\=terse command line options. The
f80dba8d
MT
3457first value is the version of the terse output format. If the output has to be
3458changed for some reason, this number will be incremented by 1 to signify that
3459change.
6820cb3b 3460
a2c95580 3461Split up, the format is as follows (comments in brackets denote when a
007c7be9 3462field was introduced or whether it's specific to some terse version):
71bfa161 3463
f80dba8d
MT
3464 ::
3465
f50fbdda 3466 terse version, fio version [v3], jobname, groupid, error
f80dba8d
MT
3467
3468 READ status::
3469
3470 Total IO (KiB), bandwidth (KiB/sec), IOPS, runtime (msec)
3471 Submission latency: min, max, mean, stdev (usec)
3472 Completion latency: min, max, mean, stdev (usec)
3473 Completion latency percentiles: 20 fields (see below)
3474 Total latency: min, max, mean, stdev (usec)
f50fbdda
TK
3475 Bw (KiB/s): min, max, aggregate percentage of total, mean, stdev, number of samples [v5]
3476 IOPS [v5]: min, max, mean, stdev, number of samples
f80dba8d
MT
3477
3478 WRITE status:
3479
3480 ::
3481
3482 Total IO (KiB), bandwidth (KiB/sec), IOPS, runtime (msec)
3483 Submission latency: min, max, mean, stdev (usec)
247823cc 3484 Completion latency: min, max, mean, stdev (usec)
f80dba8d
MT
3485 Completion latency percentiles: 20 fields (see below)
3486 Total latency: min, max, mean, stdev (usec)
f50fbdda
TK
3487 Bw (KiB/s): min, max, aggregate percentage of total, mean, stdev, number of samples [v5]
3488 IOPS [v5]: min, max, mean, stdev, number of samples
a2c95580
AH
3489
3490 TRIM status [all but version 3]:
3491
f50fbdda 3492 Fields are similar to READ/WRITE status.
f80dba8d
MT
3493
3494 CPU usage::
3495
3496 user, system, context switches, major faults, minor faults
3497
3498 I/O depths::
3499
3500 <=1, 2, 4, 8, 16, 32, >=64
3501
3502 I/O latencies microseconds::
3503
3504 <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000
3505
3506 I/O latencies milliseconds::
3507
3508 <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, 2000, >=2000
3509
a2c95580 3510 Disk utilization [v3]::
f80dba8d 3511
f50fbdda
TK
3512 disk name, read ios, write ios, read merges, write merges, read ticks, write ticks,
3513 time spent in queue, disk utilization percentage
f80dba8d
MT
3514
3515 Additional Info (dependent on continue_on_error, default off)::
3516
3517 total # errors, first error code
3518
3519 Additional Info (dependent on description being set)::
3520
3521 Text description
3522
3523Completion latency percentiles can be a grouping of up to 20 sets, so for the
3524terse output fio writes all of them. Each field will look like this::
1db92cb6 3525
f50fbdda 3526 1.00%=6112
1db92cb6 3527
f80dba8d 3528which is the Xth percentile, and the `usec` latency associated with it.
1db92cb6 3529
f50fbdda 3530For `Disk utilization`, all disks used by fio are shown. So for each disk there
f80dba8d 3531will be a disk utilization section.
f2f788dd 3532
2fc26c3d 3533Below is a single line containing short names for each of the fields in the
2831be97 3534minimal output v3, separated by semicolons::
2fc26c3d 3535
f50fbdda 3536 terse_version_3;fio_version;jobname;groupid;error;read_kb;read_bandwidth;read_iops;read_runtime_ms;read_slat_min;read_slat_max;read_slat_mean;read_slat_dev;read_clat_min;read_clat_max;read_clat_mean;read_clat_dev;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;read_lat_max;read_lat_mean;read_lat_dev;read_bw_min;read_bw_max;read_bw_agg_pct;read_bw_mean;read_bw_dev;write_kb;write_bandwidth;write_iops;write_runtime_ms;write_slat_min;write_slat_max;write_slat_mean;write_slat_dev;write_clat_min;write_clat_max;write_clat_mean;write_clat_dev;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;write_lat_max;write_lat_mean;write_lat_dev;write_bw_min;write_bw_max;write_bw_agg_pct;write_bw_mean;write_bw_dev;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
2fc26c3d 3537
25c8b9d7 3538
44c82dba
VF
3539JSON output
3540------------
3541
3542The `json` output format is intended to be both human readable and convenient
3543for automated parsing. For the most part its sections mirror those of the
3544`normal` output. The `runtime` value is reported in msec and the `bw` value is
3545reported in 1024 bytes per second units.
3546
3547
d29c4a91
VF
3548JSON+ output
3549------------
3550
3551The `json+` output format is identical to the `json` output format except that it
3552adds a full dump of the completion latency bins. Each `bins` object contains a
3553set of (key, value) pairs where keys are latency durations and values count how
3554many I/Os had completion latencies of the corresponding duration. For example,
3555consider:
3556
3557 "bins" : { "87552" : 1, "89600" : 1, "94720" : 1, "96768" : 1, "97792" : 1, "99840" : 1, "100864" : 2, "103936" : 6, "104960" : 534, "105984" : 5995, "107008" : 7529, ... }
3558
3559This data indicates that one I/O required 87,552ns to complete, two I/Os required
3560100,864ns to complete, and 7529 I/Os required 107,008ns to complete.
3561
3562Also included with fio is a Python script `fio_jsonplus_clat2csv` that takes
3563json+ output and generates CSV-formatted latency data suitable for plotting.
3564
3565The latency durations actually represent the midpoints of latency intervals.
f50fbdda 3566For details refer to :file:`stat.h`.
d29c4a91
VF
3567
3568
f80dba8d
MT
3569Trace file format
3570-----------------
3571
3572There are two trace file format that you can encounter. The older (v1) format is
3573unsupported since version 1.20-rc3 (March 2008). It will still be described
25c8b9d7
PD
3574below in case that you get an old trace and want to understand it.
3575
3576In any case the trace is a simple text file with a single action per line.
3577
3578
f80dba8d
MT
3579Trace file format v1
3580~~~~~~~~~~~~~~~~~~~~
3581
3582Each line represents a single I/O action in the following format::
3583
3584 rw, offset, length
25c8b9d7 3585
f50fbdda 3586where `rw=0/1` for read/write, and the `offset` and `length` entries being in bytes.
25c8b9d7 3587
22413915 3588This format is not supported in fio versions >= 1.20-rc3.
25c8b9d7 3589
25c8b9d7 3590
f80dba8d
MT
3591Trace file format v2
3592~~~~~~~~~~~~~~~~~~~~
25c8b9d7 3593
f80dba8d
MT
3594The second version of the trace file format was added in fio version 1.17. It
3595allows to access more then one file per trace and has a bigger set of possible
3596file actions.
25c8b9d7 3597
f80dba8d 3598The first line of the trace file has to be::
25c8b9d7 3599
f80dba8d 3600 fio version 2 iolog
25c8b9d7
PD
3601
3602Following this can be lines in two different formats, which are described below.
3603
f80dba8d 3604The file management format::
25c8b9d7 3605
f80dba8d 3606 filename action
25c8b9d7 3607
f50fbdda 3608The `filename` is given as an absolute path. The `action` can be one of these:
25c8b9d7 3609
f80dba8d 3610**add**
f50fbdda 3611 Add the given `filename` to the trace.
f80dba8d 3612**open**
f50fbdda 3613 Open the file with the given `filename`. The `filename` has to have
f80dba8d
MT
3614 been added with the **add** action before.
3615**close**
f50fbdda 3616 Close the file with the given `filename`. The file has to have been
f80dba8d
MT
3617 opened before.
3618
3619
3620The file I/O action format::
3621
3622 filename action offset length
3623
3624The `filename` is given as an absolute path, and has to have been added and
3625opened before it can be used with this format. The `offset` and `length` are
3626given in bytes. The `action` can be one of these:
3627
3628**wait**
3629 Wait for `offset` microseconds. Everything below 100 is discarded.
3630 The time is relative to the previous `wait` statement.
3631**read**
3632 Read `length` bytes beginning from `offset`.
3633**write**
3634 Write `length` bytes beginning from `offset`.
3635**sync**
3636 :manpage:`fsync(2)` the file.
3637**datasync**
3638 :manpage:`fdatasync(2)` the file.
3639**trim**
3640 Trim the given file from the given `offset` for `length` bytes.
3641
3642CPU idleness profiling
3643----------------------
3644
3645In some cases, we want to understand CPU overhead in a test. For example, we
3646test patches for the specific goodness of whether they reduce CPU usage.
3647Fio implements a balloon approach to create a thread per CPU that runs at idle
3648priority, meaning that it only runs when nobody else needs the cpu.
3649By measuring the amount of work completed by the thread, idleness of each CPU
3650can be derived accordingly.
3651
3652An unit work is defined as touching a full page of unsigned characters. Mean and
3653standard deviation of time to complete an unit work is reported in "unit work"
3654section. Options can be chosen to report detailed percpu idleness or overall
3655system idleness by aggregating percpu stats.
3656
3657
3658Verification and triggers
3659-------------------------
3660
3661Fio is usually run in one of two ways, when data verification is done. The first
3662is a normal write job of some sort with verify enabled. When the write phase has
3663completed, fio switches to reads and verifies everything it wrote. The second
3664model is running just the write phase, and then later on running the same job
3665(but with reads instead of writes) to repeat the same I/O patterns and verify
3666the contents. Both of these methods depend on the write phase being completed,
3667as fio otherwise has no idea how much data was written.
3668
3669With verification triggers, fio supports dumping the current write state to
3670local files. Then a subsequent read verify workload can load this state and know
3671exactly where to stop. This is useful for testing cases where power is cut to a
3672server in a managed fashion, for instance.
99b9a85a
JA
3673
3674A verification trigger consists of two things:
3675
f80dba8d
MT
36761) Storing the write state of each job.
36772) Executing a trigger command.
99b9a85a 3678
f80dba8d
MT
3679The write state is relatively small, on the order of hundreds of bytes to single
3680kilobytes. It contains information on the number of completions done, the last X
3681completions, etc.
99b9a85a 3682
f80dba8d
MT
3683A trigger is invoked either through creation ('touch') of a specified file in
3684the system, or through a timeout setting. If fio is run with
9207a0cb 3685:option:`--trigger-file`\= :file:`/tmp/trigger-file`, then it will continually
f80dba8d
MT
3686check for the existence of :file:`/tmp/trigger-file`. When it sees this file, it
3687will fire off the trigger (thus saving state, and executing the trigger
99b9a85a
JA
3688command).
3689
f80dba8d
MT
3690For client/server runs, there's both a local and remote trigger. If fio is
3691running as a server backend, it will send the job states back to the client for
3692safe storage, then execute the remote trigger, if specified. If a local trigger
3693is specified, the server will still send back the write state, but the client
3694will then execute the trigger.
99b9a85a 3695
f80dba8d
MT
3696Verification trigger example
3697~~~~~~~~~~~~~~~~~~~~~~~~~~~~
99b9a85a 3698
f50fbdda
TK
3699Let's say we want to run a powercut test on the remote Linux machine 'server'.
3700Our write workload is in :file:`write-test.fio`. We want to cut power to 'server' at
f80dba8d
MT
3701some point during the run, and we'll run this test from the safety or our local
3702machine, 'localbox'. On the server, we'll start the fio backend normally::
99b9a85a 3703
f80dba8d 3704 server# fio --server
99b9a85a 3705
f80dba8d 3706and on the client, we'll fire off the workload::
99b9a85a 3707
f80dba8d 3708 localbox$ fio --client=server --trigger-file=/tmp/my-trigger --trigger-remote="bash -c \"echo b > /proc/sysrq-triger\""
99b9a85a 3709
f80dba8d 3710We set :file:`/tmp/my-trigger` as the trigger file, and we tell fio to execute::
99b9a85a 3711
f80dba8d 3712 echo b > /proc/sysrq-trigger
99b9a85a 3713
f80dba8d
MT
3714on the server once it has received the trigger and sent us the write state. This
3715will work, but it's not **really** cutting power to the server, it's merely
3716abruptly rebooting it. If we have a remote way of cutting power to the server
3717through IPMI or similar, we could do that through a local trigger command
4502cb42 3718instead. Let's assume we have a script that does IPMI reboot of a given hostname,
f80dba8d
MT
3719ipmi-reboot. On localbox, we could then have run fio with a local trigger
3720instead::
99b9a85a 3721
f80dba8d 3722 localbox$ fio --client=server --trigger-file=/tmp/my-trigger --trigger="ipmi-reboot server"
99b9a85a 3723
f80dba8d
MT
3724For this case, fio would wait for the server to send us the write state, then
3725execute ``ipmi-reboot server`` when that happened.
3726
3727Loading verify state
3728~~~~~~~~~~~~~~~~~~~~
3729
4502cb42 3730To load stored write state, a read verification job file must contain the
f80dba8d 3731:option:`verify_state_load` option. If that is set, fio will load the previously
99b9a85a 3732stored state. For a local fio run this is done by loading the files directly,
f80dba8d
MT
3733and on a client/server run, the server backend will ask the client to send the
3734files over and load them from there.
a3ae5b05
JA
3735
3736
f80dba8d
MT
3737Log File Formats
3738----------------
a3ae5b05
JA
3739
3740Fio supports a variety of log file formats, for logging latencies, bandwidth,
3741and IOPS. The logs share a common format, which looks like this:
3742
5a83478f
SW
3743 *time* (`msec`), *value*, *data direction*, *block size* (`bytes`),
3744 *offset* (`bytes`)
a3ae5b05 3745
5a83478f 3746*Time* for the log entry is always in milliseconds. The *value* logged depends
a3ae5b05
JA
3747on the type of log, it will be one of the following:
3748
f80dba8d 3749 **Latency log**
168bb587 3750 Value is latency in nsecs
f80dba8d
MT
3751 **Bandwidth log**
3752 Value is in KiB/sec
3753 **IOPS log**
3754 Value is IOPS
3755
3756*Data direction* is one of the following:
3757
3758 **0**
3759 I/O is a READ
3760 **1**
3761 I/O is a WRITE
3762 **2**
3763 I/O is a TRIM
3764
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3765The entry's *block size* is always in bytes. The *offset* is the offset, in bytes,
3766from the start of the file, for that particular I/O. The logging of the offset can be
3767toggled with :option:`log_offset`.
f80dba8d 3768
6fc82095 3769Fio defaults to logging every individual I/O. When IOPS are logged for individual
5a83478f 3770I/Os the *value* entry will always be 1. If windowed logging is enabled through
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3771:option:`log_avg_msec`, fio logs the average values over the specified period of time.
3772If windowed logging is enabled and :option:`log_max_value` is set, then fio logs
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3773maximum values in that window instead of averages. Since *data direction*, *block
3774size* and *offset* are per-I/O values, if windowed logging is enabled they
3775aren't applicable and will be 0.
f80dba8d 3776
b8f7e412 3777Client/Server
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3778-------------
3779
3780Normally fio is invoked as a stand-alone application on the machine where the
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3781I/O workload should be generated. However, the backend and frontend of fio can
3782be run separately i.e., the fio server c