Option for changing log files to use Unix epoch instead of being
[fio.git] / HOWTO
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1Table of contents
2-----------------
3
41. Overview
52. How fio works
63. Running fio
74. Job file format
85. Detailed list of parameters
96. Normal output
107. Terse output
25c8b9d7 118. Trace file format
43f09da1 129. CPU idleness profiling
29dbd1e5 1310. Verification and triggers
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1411. Log File Formats
15
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16
171.0 Overview and history
18------------------------
19fio was originally written to save me the hassle of writing special test
20case programs when I wanted to test a specific workload, either for
21performance reasons or to find/reproduce a bug. The process of writing
22such a test app can be tiresome, especially if you have to do it often.
23Hence I needed a tool that would be able to simulate a given io workload
24without resorting to writing a tailored test case again and again.
25
26A test work load is difficult to define, though. There can be any number
27of processes or threads involved, and they can each be using their own
28way of generating io. You could have someone dirtying large amounts of
29memory in an memory mapped file, or maybe several threads issuing
30reads using asynchronous io. fio needed to be flexible enough to
31simulate both of these cases, and many more.
32
332.0 How fio works
34-----------------
35The first step in getting fio to simulate a desired io workload, is
36writing a job file describing that specific setup. A job file may contain
37any number of threads and/or files - the typical contents of the job file
38is a global section defining shared parameters, and one or more job
39sections describing the jobs involved. When run, fio parses this file
40and sets everything up as described. If we break down a job from top to
41bottom, it contains the following basic parameters:
42
43 IO type Defines the io pattern issued to the file(s).
44 We may only be reading sequentially from this
45 file(s), or we may be writing randomly. Or even
46 mixing reads and writes, sequentially or randomly.
47
48 Block size In how large chunks are we issuing io? This may be
49 a single value, or it may describe a range of
50 block sizes.
51
52 IO size How much data are we going to be reading/writing.
53
54 IO engine How do we issue io? We could be memory mapping the
55 file, we could be using regular read/write, we
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56 could be using splice, async io, or even SG
57 (SCSI generic sg).
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6c219763 59 IO depth If the io engine is async, how large a queuing
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60 depth do we want to maintain?
61
62 IO type Should we be doing buffered io, or direct/raw io?
63
64 Num files How many files are we spreading the workload over.
65
66 Num threads How many threads or processes should we spread
67 this workload over.
66c098b8 68
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69The above are the basic parameters defined for a workload, in addition
70there's a multitude of parameters that modify other aspects of how this
71job behaves.
72
73
743.0 Running fio
75---------------
76See the README file for command line parameters, there are only a few
77of them.
78
79Running fio is normally the easiest part - you just give it the job file
80(or job files) as parameters:
81
82$ fio job_file
83
84and it will start doing what the job_file tells it to do. You can give
85more than one job file on the command line, fio will serialize the running
86of those files. Internally that is the same as using the 'stonewall'
550b1db6 87parameter described in the parameter section.
71bfa161 88
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89If the job file contains only one job, you may as well just give the
90parameters on the command line. The command line parameters are identical
91to the job parameters, with a few extra that control global parameters
92(see README). For example, for the job file parameter iodepth=2, the
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93mirror command line option would be --iodepth 2 or --iodepth=2. You can
94also use the command line for giving more than one job entry. For each
95--name option that fio sees, it will start a new job with that name.
96Command line entries following a --name entry will apply to that job,
97until there are no more entries or a new --name entry is seen. This is
98similar to the job file options, where each option applies to the current
99job until a new [] job entry is seen.
b4692828 100
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101fio does not need to run as root, except if the files or devices specified
102in the job section requires that. Some other options may also be restricted,
6c219763 103such as memory locking, io scheduler switching, and decreasing the nice value.
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104
105
1064.0 Job file format
107-------------------
108As previously described, fio accepts one or more job files describing
109what it is supposed to do. The job file format is the classic ini file,
110where the names enclosed in [] brackets define the job name. You are free
111to use any ascii name you want, except 'global' which has special meaning.
112A global section sets defaults for the jobs described in that file. A job
113may override a global section parameter, and a job file may even have
114several global sections if so desired. A job is only affected by a global
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115section residing above it. If the first character in a line is a ';' or a
116'#', the entire line is discarded as a comment.
71bfa161 117
3c54bc46 118So let's look at a really simple job file that defines two processes, each
b22989b9 119randomly reading from a 128MB file.
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120
121; -- start job file --
122[global]
123rw=randread
124size=128m
125
126[job1]
127
128[job2]
129
130; -- end job file --
131
132As you can see, the job file sections themselves are empty as all the
133described parameters are shared. As no filename= option is given, fio
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134makes up a filename for each of the jobs as it sees fit. On the command
135line, this job would look as follows:
136
137$ fio --name=global --rw=randread --size=128m --name=job1 --name=job2
138
71bfa161 139
3c54bc46 140Let's look at an example that has a number of processes writing randomly
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141to files.
142
143; -- start job file --
144[random-writers]
145ioengine=libaio
146iodepth=4
147rw=randwrite
148bs=32k
149direct=0
150size=64m
151numjobs=4
152
153; -- end job file --
154
155Here we have no global section, as we only have one job defined anyway.
156We want to use async io here, with a depth of 4 for each file. We also
b22989b9 157increased the buffer size used to 32KB and define numjobs to 4 to
71bfa161 158fork 4 identical jobs. The result is 4 processes each randomly writing
b22989b9 159to their own 64MB file. Instead of using the above job file, you could
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160have given the parameters on the command line. For this case, you would
161specify:
162
163$ fio --name=random-writers --ioengine=libaio --iodepth=4 --rw=randwrite --bs=32k --direct=0 --size=64m --numjobs=4
71bfa161 164
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165When fio is utilized as a basis of any reasonably large test suite, it might be
166desirable to share a set of standardized settings across multiple job files.
167Instead of copy/pasting such settings, any section may pull in an external
168.fio file with 'include filename' directive, as in the following example:
169
170; -- start job file including.fio --
171[global]
172filename=/tmp/test
173filesize=1m
174include glob-include.fio
175
176[test]
177rw=randread
178bs=4k
179time_based=1
180runtime=10
181include test-include.fio
182; -- end job file including.fio --
183
184; -- start job file glob-include.fio --
185thread=1
186group_reporting=1
187; -- end job file glob-include.fio --
188
189; -- start job file test-include.fio --
190ioengine=libaio
191iodepth=4
192; -- end job file test-include.fio --
193
194Settings pulled into a section apply to that section only (except global
195section). Include directives may be nested in that any included file may
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196contain further include directive(s). Include files may not contain []
197sections.
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198
199
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2004.1 Environment variables
201-------------------------
202
3c54bc46 203fio also supports environment variable expansion in job files. Any
4fbe1860 204sub-string of the form "${VARNAME}" as part of an option value (in other
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205words, on the right of the `='), will be expanded to the value of the
206environment variable called VARNAME. If no such environment variable
207is defined, or VARNAME is the empty string, the empty string will be
208substituted.
209
210As an example, let's look at a sample fio invocation and job file:
211
212$ SIZE=64m NUMJOBS=4 fio jobfile.fio
213
214; -- start job file --
215[random-writers]
216rw=randwrite
217size=${SIZE}
218numjobs=${NUMJOBS}
219; -- end job file --
220
221This will expand to the following equivalent job file at runtime:
222
223; -- start job file --
224[random-writers]
225rw=randwrite
226size=64m
227numjobs=4
228; -- end job file --
229
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230fio ships with a few example job files, you can also look there for
231inspiration.
232
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2334.2 Reserved keywords
234---------------------
235
236Additionally, fio has a set of reserved keywords that will be replaced
237internally with the appropriate value. Those keywords are:
238
239$pagesize The architecture page size of the running system
240$mb_memory Megabytes of total memory in the system
241$ncpus Number of online available CPUs
242
243These can be used on the command line or in the job file, and will be
244automatically substituted with the current system values when the job
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245is run. Simple math is also supported on these keywords, so you can
246perform actions like:
247
248size=8*$mb_memory
249
250and get that properly expanded to 8 times the size of memory in the
251machine.
74929ac2 252
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253
2545.0 Detailed list of parameters
255-------------------------------
256
257This section describes in details each parameter associated with a job.
258Some parameters take an option of a given type, such as an integer or
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259a string. Anywhere a numeric value is required, an arithmetic expression
260may be used, provided it is surrounded by parentheses. Supported operators
261are:
262
263 addition (+)
264 subtraction (-)
265 multiplication (*)
266 division (/)
267 modulus (%)
268 exponentiation (^)
269
270For time values in expressions, units are microseconds by default. This is
271different than for time values not in expressions (not enclosed in
272parentheses). The following types are used:
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273
274str String. This is a sequence of alpha characters.
b09da8fa 275time Integer with possible time suffix. In seconds unless otherwise
e417fd66 276 specified, use eg 10m for 10 minutes. Accepts s/m/h for seconds,
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277 minutes, and hours, and accepts 'ms' (or 'msec') for milliseconds,
278 and 'us' (or 'usec') for microseconds.
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279int SI integer. A whole number value, which may contain a suffix
280 describing the base of the number. Accepted suffixes are k/m/g/t/p,
281 meaning kilo, mega, giga, tera, and peta. The suffix is not case
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282 sensitive, and you may also include trailing 'b' (eg 'kb' is the same
283 as 'k'). So if you want to specify 4096, you could either write
b09da8fa 284 out '4096' or just give 4k. The suffixes signify base 2 values, so
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285 1024 is 1k and 1024k is 1m and so on, unless the suffix is explicitly
286 set to a base 10 value using 'kib', 'mib', 'gib', etc. If that is the
287 case, then 1000 is used as the multiplier. This can be handy for
288 disks, since manufacturers generally use base 10 values when listing
289 the capacity of a drive. If the option accepts an upper and lower
290 range, use a colon ':' or minus '-' to separate such values. May also
291 include a prefix to indicate numbers base. If 0x is used, the number
292 is assumed to be hexadecimal. See irange.
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293bool Boolean. Usually parsed as an integer, however only defined for
294 true and false (1 and 0).
b09da8fa 295irange Integer range with suffix. Allows value range to be given, such
bf9a3edb 296 as 1024-4096. A colon may also be used as the separator, eg
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297 1k:4k. If the option allows two sets of ranges, they can be
298 specified with a ',' or '/' delimiter: 1k-4k/8k-32k. Also see
f7fa2653 299 int.
83349190 300float_list A list of floating numbers, separated by a ':' character.
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301
302With the above in mind, here follows the complete list of fio job
303parameters.
304
305name=str ASCII name of the job. This may be used to override the
306 name printed by fio for this job. Otherwise the job
c2b1e753 307 name is used. On the command line this parameter has the
6c219763 308 special purpose of also signaling the start of a new
c2b1e753 309 job.
71bfa161 310
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311wait_for=str Specifies the name of the already defined job to wait
312 for. Single waitee name only may be specified. If set, the job
313 won't be started until all workers of the waitee job are done.
314
315 Wait_for operates on the job name basis, so there are a few
316 limitations. First, the waitee must be defined prior to the
317 waiter job (meaning no forward references). Second, if a job
318 is being referenced as a waitee, it must have a unique name
319 (no duplicate waitees).
320
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321description=str Text description of the job. Doesn't do anything except
322 dump this text description when this job is run. It's
323 not parsed.
324
3776041e 325directory=str Prefix filenames with this directory. Used to place files
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326 in a different location than "./". See the 'filename' option
327 for escaping certain characters.
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328
329filename=str Fio normally makes up a filename based on the job name,
330 thread number, and file number. If you want to share
331 files between threads in a job or several jobs, specify
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332 a filename for each of them to override the default.
333 If the ioengine is file based, you can specify a number of
334 files by separating the names with a ':' colon. So if you
335 wanted a job to open /dev/sda and /dev/sdb as the two working
336 files, you would use filename=/dev/sda:/dev/sdb. On Windows,
337 disk devices are accessed as \\.\PhysicalDrive0 for the first
338 device, \\.\PhysicalDrive1 for the second etc. Note: Windows
339 and FreeBSD prevent write access to areas of the disk
340 containing in-use data (e.g. filesystems).
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341 If the wanted filename does need to include a colon, then
342 escape that with a '\' character. For instance, if the filename
343 is "/dev/dsk/foo@3,0:c", then you would use
344 filename="/dev/dsk/foo@3,0\:c". '-' is a reserved name, meaning
345 stdin or stdout. Which of the two depends on the read/write
346 direction set.
71bfa161 347
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348filename_format=str
349 If sharing multiple files between jobs, it is usually necessary
350 to have fio generate the exact names that you want. By default,
351 fio will name a file based on the default file format
352 specification of jobname.jobnumber.filenumber. With this
353 option, that can be customized. Fio will recognize and replace
354 the following keywords in this string:
355
356 $jobname
357 The name of the worker thread or process.
358
359 $jobnum
360 The incremental number of the worker thread or
361 process.
362
363 $filenum
364 The incremental number of the file for that worker
365 thread or process.
366
367 To have dependent jobs share a set of files, this option can
368 be set to have fio generate filenames that are shared between
369 the two. For instance, if testfiles.$filenum is specified,
370 file number 4 for any job will be named testfiles.4. The
371 default of $jobname.$jobnum.$filenum will be used if
372 no other format specifier is given.
373
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374unique_filename=bool To avoid collisions between networked clients, fio
375 defaults to prefixing any generated filenames (with a directory
376 specified) with the source of the client connecting. To disable
377 this behavior, set this option to 0.
378
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379opendir=str Tell fio to recursively add any file it can find in this
380 directory and down the file system tree.
381
3776041e 382lockfile=str Fio defaults to not locking any files before it does
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383 IO to them. If a file or file descriptor is shared, fio
384 can serialize IO to that file to make the end result
385 consistent. This is usual for emulating real workloads that
386 share files. The lock modes are:
387
388 none No locking. The default.
389 exclusive Only one thread/process may do IO,
390 excluding all others.
391 readwrite Read-write locking on the file. Many
392 readers may access the file at the
393 same time, but writes get exclusive
394 access.
395
d3aad8f2 396readwrite=str
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397rw=str Type of io pattern. Accepted values are:
398
399 read Sequential reads
400 write Sequential writes
401 randwrite Random writes
402 randread Random reads
10b023db 403 rw,readwrite Sequential mixed reads and writes
71bfa161 404 randrw Random mixed reads and writes
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405 trimwrite Mixed trims and writes. Blocks will be
406 trimmed first, then written to.
71bfa161 407
38f8c318 408 Fio defaults to read if the option is not specified.
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409 For the mixed io types, the default is to split them 50/50.
410 For certain types of io the result may still be skewed a bit,
211097b2 411 since the speed may be different. It is possible to specify
38dad62d 412 a number of IO's to do before getting a new offset, this is
892ea9bd 413 done by appending a ':<nr>' to the end of the string given.
38dad62d 414 For a random read, it would look like 'rw=randread:8' for
059b0802 415 passing in an offset modifier with a value of 8. If the
ddb754db 416 suffix is used with a sequential IO pattern, then the value
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417 specified will be added to the generated offset for each IO.
418 For instance, using rw=write:4k will skip 4k for every
419 write. It turns sequential IO into sequential IO with holes.
420 See the 'rw_sequencer' option.
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421
422rw_sequencer=str If an offset modifier is given by appending a number to
423 the rw=<str> line, then this option controls how that
424 number modifies the IO offset being generated. Accepted
425 values are:
426
427 sequential Generate sequential offset
428 identical Generate the same offset
429
430 'sequential' is only useful for random IO, where fio would
431 normally generate a new random offset for every IO. If you
432 append eg 8 to randread, you would get a new random offset for
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433 every 8 IO's. The result would be a seek for only every 8
434 IO's, instead of for every IO. Use rw=randread:8 to specify
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435 that. As sequential IO is already sequential, setting
436 'sequential' for that would not result in any differences.
437 'identical' behaves in a similar fashion, except it sends
438 the same offset 8 number of times before generating a new
439 offset.
71bfa161 440
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441kb_base=int The base unit for a kilobyte. The defacto base is 2^10, 1024.
442 Storage manufacturers like to use 10^3 or 1000 as a base
443 ten unit instead, for obvious reasons. Allow values are
444 1024 or 1000, with 1024 being the default.
445
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446unified_rw_reporting=bool Fio normally reports statistics on a per
447 data direction basis, meaning that read, write, and trim are
448 accounted and reported separately. If this option is set,
449 the fio will sum the results and report them as "mixed"
450 instead.
451
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452randrepeat=bool For random IO workloads, seed the generator in a predictable
453 way so that results are repeatable across repetitions.
40fe5e7b 454 Defaults to true.
ee738499 455
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456randseed=int Seed the random number generators based on this seed value, to
457 be able to control what sequence of output is being generated.
458 If not set, the random sequence depends on the randrepeat
459 setting.
460
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461fallocate=str Whether pre-allocation is performed when laying down files.
462 Accepted values are:
463
464 none Do not pre-allocate space
465 posix Pre-allocate via posix_fallocate()
466 keep Pre-allocate via fallocate() with
467 FALLOC_FL_KEEP_SIZE set
468 0 Backward-compatible alias for 'none'
469 1 Backward-compatible alias for 'posix'
470
471 May not be available on all supported platforms. 'keep' is only
472 available on Linux.If using ZFS on Solaris this must be set to
473 'none' because ZFS doesn't support it. Default: 'posix'.
7bc8c2cf 474
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475fadvise_hint=bool By default, fio will use fadvise() to advise the kernel
476 on what IO patterns it is likely to issue. Sometimes you
477 want to test specific IO patterns without telling the
478 kernel about it, in which case you can disable this option.
479 If set, fio will use POSIX_FADV_SEQUENTIAL for sequential
480 IO and POSIX_FADV_RANDOM for random IO.
481
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482fadvise_stream=int Notify the kernel what write stream ID to place these
483 writes under. Only supported on Linux. Note, this option
484 may change going forward.
485
f7fa2653 486size=int The total size of file io for this job. Fio will run until
7616cafe 487 this many bytes has been transferred, unless runtime is
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488 limited by other options (such as 'runtime', for instance,
489 or increased/decreased by 'io_size'). Unless specific nrfiles
490 and filesize options are given, fio will divide this size
491 between the available files specified by the job. If not set,
492 fio will use the full size of the given files or devices.
493 If the files do not exist, size must be given. It is also
494 possible to give size as a percentage between 1 and 100. If
495 size=20% is given, fio will use 20% of the full size of the
496 given files or devices.
497
498io_size=int
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499io_limit=int Normally fio operates within the region set by 'size', which
500 means that the 'size' option sets both the region and size of
501 IO to be performed. Sometimes that is not what you want. With
502 this option, it is possible to define just the amount of IO
503 that fio should do. For instance, if 'size' is set to 20G and
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504 'io_size' is set to 5G, fio will perform IO within the first
505 20G but exit when 5G have been done. The opposite is also
506 possible - if 'size' is set to 20G, and 'io_size' is set to
507 40G, then fio will do 40G of IO within the 0..20G region.
77731b29 508
f7fa2653 509filesize=int Individual file sizes. May be a range, in which case fio
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510 will select sizes for files at random within the given range
511 and limited to 'size' in total (if that is given). If not
512 given, each created file is the same size.
513
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514file_append=bool Perform IO after the end of the file. Normally fio will
515 operate within the size of a file. If this option is set, then
516 fio will append to the file instead. This has identical
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517 behavior to setting offset to the size of a file. This option
518 is ignored on non-regular files.
bedc9dc2 519
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520fill_device=bool
521fill_fs=bool Sets size to something really large and waits for ENOSPC (no
aa31f1f1 522 space left on device) as the terminating condition. Only makes
de98bd30 523 sense with sequential write. For a read workload, the mount
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524 point will be filled first then IO started on the result. This
525 option doesn't make sense if operating on a raw device node,
526 since the size of that is already known by the file system.
527 Additionally, writing beyond end-of-device will not return
528 ENOSPC there.
aa31f1f1 529
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530blocksize=int
531bs=int The block size used for the io units. Defaults to 4k. Values
532 can be given for both read and writes. If a single int is
533 given, it will apply to both. If a second int is specified
f90eff5a 534 after a comma, it will apply to writes only. In other words,
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535 the format is either bs=read_and_write or bs=read,write,trim.
536 bs=4k,8k will thus use 4k blocks for reads, 8k blocks for
537 writes, and 8k for trims. You can terminate the list with
538 a trailing comma. bs=4k,8k, would use the default value for
539 trims.. If you only wish to set the write size, you
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540 can do so by passing an empty read size - bs=,8k will set
541 8k for writes and leave the read default value.
a00735e6 542
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543blockalign=int
544ba=int At what boundary to align random IO offsets. Defaults to
545 the same as 'blocksize' the minimum blocksize given.
546 Minimum alignment is typically 512b for using direct IO,
547 though it usually depends on the hardware block size. This
548 option is mutually exclusive with using a random map for
549 files, so it will turn off that option.
550
d3aad8f2 551blocksize_range=irange
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552bsrange=irange Instead of giving a single block size, specify a range
553 and fio will mix the issued io block sizes. The issued
554 io unit will always be a multiple of the minimum value
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555 given (also see bs_unaligned). Applies to both reads and
556 writes, however a second range can be given after a comma.
557 See bs=.
a00735e6 558
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559bssplit=str Sometimes you want even finer grained control of the
560 block sizes issued, not just an even split between them.
561 This option allows you to weight various block sizes,
562 so that you are able to define a specific amount of
563 block sizes issued. The format for this option is:
564
565 bssplit=blocksize/percentage:blocksize/percentage
566
567 for as many block sizes as needed. So if you want to define
568 a workload that has 50% 64k blocks, 10% 4k blocks, and
569 40% 32k blocks, you would write:
570
571 bssplit=4k/10:64k/50:32k/40
572
573 Ordering does not matter. If the percentage is left blank,
574 fio will fill in the remaining values evenly. So a bssplit
575 option like this one:
576
577 bssplit=4k/50:1k/:32k/
578
579 would have 50% 4k ios, and 25% 1k and 32k ios. The percentages
580 always add up to 100, if bssplit is given a range that adds
581 up to more, it will error out.
582
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583 bssplit also supports giving separate splits to reads and
584 writes. The format is identical to what bs= accepts. You
585 have to separate the read and write parts with a comma. So
586 if you want a workload that has 50% 2k reads and 50% 4k reads,
587 while having 90% 4k writes and 10% 8k writes, you would
588 specify:
589
892ea9bd 590 bssplit=2k/50:4k/50,4k/90:8k/10
720e84ad 591
d3aad8f2 592blocksize_unaligned
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593bs_unaligned If this option is given, any byte size value within bsrange
594 may be used as a block range. This typically wont work with
595 direct IO, as that normally requires sector alignment.
71bfa161 596
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597bs_is_seq_rand If this option is set, fio will use the normal read,write
598 blocksize settings as sequential,random instead. Any random
599 read or write will use the WRITE blocksize settings, and any
600 sequential read or write will use the READ blocksize setting.
601
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602zero_buffers If this option is given, fio will init the IO buffers to
603 all zeroes. The default is to fill them with random data.
604
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605refill_buffers If this option is given, fio will refill the IO buffers
606 on every submit. The default is to only fill it at init
607 time and reuse that data. Only makes sense if zero_buffers
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608 isn't specified, naturally. If data verification is enabled,
609 refill_buffers is also automatically enabled.
5973cafb 610
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611scramble_buffers=bool If refill_buffers is too costly and the target is
612 using data deduplication, then setting this option will
613 slightly modify the IO buffer contents to defeat normal
614 de-dupe attempts. This is not enough to defeat more clever
615 block compression attempts, but it will stop naive dedupe of
616 blocks. Default: true.
617
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618buffer_compress_percentage=int If this is set, then fio will attempt to
619 provide IO buffer content (on WRITEs) that compress to
620 the specified level. Fio does this by providing a mix of
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621 random data and a fixed pattern. The fixed pattern is either
622 zeroes, or the pattern specified by buffer_pattern. If the
623 pattern option is used, it might skew the compression ratio
624 slightly. Note that this is per block size unit, for file/disk
625 wide compression level that matches this setting, you'll also
626 want to set refill_buffers.
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627
628buffer_compress_chunk=int See buffer_compress_percentage. This
629 setting allows fio to manage how big the ranges of random
630 data and zeroed data is. Without this set, fio will
631 provide buffer_compress_percentage of blocksize random
632 data, followed by the remaining zeroed. With this set
633 to some chunk size smaller than the block size, fio can
634 alternate random and zeroed data throughout the IO
635 buffer.
636
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637buffer_pattern=str If set, fio will fill the io buffers with this
638 pattern. If not set, the contents of io buffers is defined by
639 the other options related to buffer contents. The setting can
640 be any pattern of bytes, and can be prefixed with 0x for hex
641 values. It may also be a string, where the string must then
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642 be wrapped with "", e.g.:
643
644 buffer_pattern="abcd"
645 or
646 buffer_pattern=-12
647 or
648 buffer_pattern=0xdeadface
649
650 Also you can combine everything together in any order:
651 buffer_pattern=0xdeadface"abcd"-12
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652
653dedupe_percentage=int If set, fio will generate this percentage of
654 identical buffers when writing. These buffers will be
655 naturally dedupable. The contents of the buffers depend on
656 what other buffer compression settings have been set. It's
657 possible to have the individual buffers either fully
658 compressible, or not at all. This option only controls the
659 distribution of unique buffers.
ce35b1ec 660
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661nrfiles=int Number of files to use for this job. Defaults to 1.
662
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663openfiles=int Number of files to keep open at the same time. Defaults to
664 the same as nrfiles, can be set smaller to limit the number
665 simultaneous opens.
666
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667file_service_type=str Defines how fio decides which file from a job to
668 service next. The following types are defined:
669
670 random Just choose a file at random.
671
672 roundrobin Round robin over open files. This
673 is the default.
674
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675 sequential Finish one file before moving on to
676 the next. Multiple files can still be
677 open depending on 'openfiles'.
678
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679 zipf Use a zipfian distribution to decide what file
680 to access.
681
682 pareto Use a pareto distribution to decide what file
683 to access.
684
685 gauss Use a gaussian (normal) distribution to decide
686 what file to access.
687
688 For random, roundrobin, and sequential, a postfix can be
689 appended to tell fio how many I/Os to issue before switching
690 to a new file. For example, specifying
691 'file_service_type=random:8' would cause fio to issue 8 I/Os
692 before selecting a new file at random. For the non-uniform
693 distributions, a floating point postfix can be given to
694 influence how the distribution is skewed. See
695 'random_distribution' for a description of how that would work.
1907dbc6 696
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697ioengine=str Defines how the job issues io to the file. The following
698 types are defined:
699
700 sync Basic read(2) or write(2) io. lseek(2) is
701 used to position the io location.
702
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703 psync Basic pread(2) or pwrite(2) io. Default on all
704 supported operating systems except for Windows.
a31041ea 705
e05af9e5 706 vsync Basic readv(2) or writev(2) IO.
1d2af02a 707
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708 pvsync Basic preadv(2) or pwritev(2) IO.
709
82e65aec 710 pvsync2 Basic preadv2(2) or pwritev2(2) IO.
a46c5e01 711
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712 libaio Linux native asynchronous io. Note that Linux
713 may only support queued behaviour with
714 non-buffered IO (set direct=1 or buffered=0).
de890a1e 715 This engine defines engine specific options.
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716
717 posixaio glibc posix asynchronous io.
718
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719 solarisaio Solaris native asynchronous io.
720
03e20d68 721 windowsaio Windows native asynchronous io.
38f8c318 722 Default on Windows.
03e20d68 723
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724 mmap File is memory mapped and data copied
725 to/from using memcpy(3).
726
727 splice splice(2) is used to transfer the data and
728 vmsplice(2) to transfer data from user
729 space to the kernel.
730
731 sg SCSI generic sg v3 io. May either be
6c219763 732 synchronous using the SG_IO ioctl, or if
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733 the target is an sg character device
734 we use read(2) and write(2) for asynchronous
735 io.
736
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737 null Doesn't transfer any data, just pretends
738 to. This is mainly used to exercise fio
739 itself and for debugging/testing purposes.
740
ed92ac0c 741 net Transfer over the network to given host:port.
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742 Depending on the protocol used, the hostname,
743 port, listen and filename options are used to
744 specify what sort of connection to make, while
745 the protocol option determines which protocol
746 will be used.
747 This engine defines engine specific options.
ed92ac0c 748
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749 netsplice Like net, but uses splice/vmsplice to
750 map data and send/receive.
de890a1e 751 This engine defines engine specific options.
9cce02e8 752
53aec0a4 753 cpuio Doesn't transfer any data, but burns CPU
ba0fbe10 754 cycles according to the cpuload= and
e0f01317 755 cpuchunks= options. Setting cpuload=85
ba0fbe10 756 will cause that job to do nothing but burn
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757 85% of the CPU. In case of SMP machines,
758 use numjobs=<no_of_cpu> to get desired CPU
759 usage, as the cpuload only loads a single
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760 CPU at the desired rate. A job never finishes
761 unless there is at least one non-cpuio job.
ba0fbe10 762
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763 guasi The GUASI IO engine is the Generic Userspace
764 Asyncronous Syscall Interface approach
765 to async IO. See
766
767 http://www.xmailserver.org/guasi-lib.html
768
769 for more info on GUASI.
770
21b8aee8 771 rdma The RDMA I/O engine supports both RDMA
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772 memory semantics (RDMA_WRITE/RDMA_READ) and
773 channel semantics (Send/Recv) for the
774 InfiniBand, RoCE and iWARP protocols.
21b8aee8 775
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776 falloc IO engine that does regular fallocate to
777 simulate data transfer as fio ioengine.
778 DDIR_READ does fallocate(,mode = keep_size,)
779 DDIR_WRITE does fallocate(,mode = 0)
780 DDIR_TRIM does fallocate(,mode = punch_hole)
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781
782 e4defrag IO engine that does regular EXT4_IOC_MOVE_EXT
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783 ioctls to simulate defragment activity in
784 request to DDIR_WRITE event
785
786 rbd IO engine supporting direct access to Ceph
787 Rados Block Devices (RBD) via librbd without
788 the need to use the kernel rbd driver. This
789 ioengine defines engine specific options.
790
791 gfapi Using Glusterfs libgfapi sync interface to
792 direct access to Glusterfs volumes without
793 options.
794
795 gfapi_async Using Glusterfs libgfapi async interface
796 to direct access to Glusterfs volumes without
797 having to go through FUSE. This ioengine
798 defines engine specific options.
0981fd71 799
b74e419e 800 libhdfs Read and write through Hadoop (HDFS).
a3f001f5 801 This engine interprets offsets a little
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802 differently. In HDFS, files once created
803 cannot be modified. So random writes are not
804 possible. To imitate this, libhdfs engine
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805 creates bunch of small files, and engine will
806 pick a file out of those files based on the
807 offset enerated by fio backend. Each jobs uses
808 it's own connection to HDFS.
1b10477b 809
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810 mtd Read, write and erase an MTD character device
811 (e.g., /dev/mtd0). Discards are treated as
812 erases. Depending on the underlying device
813 type, the I/O may have to go in a certain
814 pattern, e.g., on NAND, writing sequentially
815 to erase blocks and discarding before
816 overwriting. The writetrim mode works well
817 for this constraint.
818
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819 pmemblk Read and write through the NVML libpmemblk
820 interface.
821
8a7bd877
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822 external Prefix to specify loading an external
823 IO engine object file. Append the engine
824 filename, eg ioengine=external:/tmp/foo.o
825 to load ioengine foo.o in /tmp.
826
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827iodepth=int This defines how many io units to keep in flight against
828 the file. The default is 1 for each file defined in this
829 job, can be overridden with a larger value for higher
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830 concurrency. Note that increasing iodepth beyond 1 will not
831 affect synchronous ioengines (except for small degress when
9b836561 832 verify_async is in use). Even async engines may impose OS
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833 restrictions causing the desired depth not to be achieved.
834 This may happen on Linux when using libaio and not setting
835 direct=1, since buffered IO is not async on that OS. Keep an
836 eye on the IO depth distribution in the fio output to verify
837 that the achieved depth is as expected. Default: 1.
71bfa161 838
4950421a 839iodepth_batch_submit=int
cb5ab512 840iodepth_batch=int This defines how many pieces of IO to submit at once.
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841 It defaults to 1 which means that we submit each IO
842 as soon as it is available, but can be raised to submit
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843 bigger batches of IO at the time. If it is set to 0 the iodepth
844 value will be used.
cb5ab512 845
82407585 846iodepth_batch_complete_min=int
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JA
847iodepth_batch_complete=int This defines how many pieces of IO to retrieve
848 at once. It defaults to 1 which means that we'll ask
849 for a minimum of 1 IO in the retrieval process from
850 the kernel. The IO retrieval will go on until we
851 hit the limit set by iodepth_low. If this variable is
852 set to 0, then fio will always check for completed
853 events before queuing more IO. This helps reduce
854 IO latency, at the cost of more retrieval system calls.
855
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856iodepth_batch_complete_max=int This defines maximum pieces of IO to
857 retrieve at once. This variable should be used along with
858 iodepth_batch_complete_min=int variable, specifying the range
859 of min and max amount of IO which should be retrieved. By default
860 it is equal to iodepth_batch_complete_min value.
861
862 Example #1:
863
864 iodepth_batch_complete_min=1
865 iodepth_batch_complete_max=<iodepth>
866
867 which means that we will retrieve at leat 1 IO and up to the
868 whole submitted queue depth. If none of IO has been completed
869 yet, we will wait.
870
871 Example #2:
872
873 iodepth_batch_complete_min=0
874 iodepth_batch_complete_max=<iodepth>
875
876 which means that we can retrieve up to the whole submitted
877 queue depth, but if none of IO has been completed yet, we will
878 NOT wait and immediately exit the system call. In this example
879 we simply do polling.
880
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881iodepth_low=int The low water mark indicating when to start filling
882 the queue again. Defaults to the same as iodepth, meaning
883 that fio will attempt to keep the queue full at all times.
884 If iodepth is set to eg 16 and iodepth_low is set to 4, then
885 after fio has filled the queue of 16 requests, it will let
886 the depth drain down to 4 before starting to fill it again.
887
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888io_submit_mode=str This option controls how fio submits the IO to
889 the IO engine. The default is 'inline', which means that the
890 fio job threads submit and reap IO directly. If set to
891 'offload', the job threads will offload IO submission to a
892 dedicated pool of IO threads. This requires some coordination
893 and thus has a bit of extra overhead, especially for lower
894 queue depth IO where it can increase latencies. The benefit
895 is that fio can manage submission rates independently of
896 the device completion rates. This avoids skewed latency
897 reporting if IO gets back up on the device side (the
898 coordinated omission problem).
899
71bfa161 900direct=bool If value is true, use non-buffered io. This is usually
9b836561 901 O_DIRECT. Note that ZFS on Solaris doesn't support direct io.
93bcfd20 902 On Windows the synchronous ioengines don't support direct io.
76a43db4 903
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CM
904atomic=bool If value is true, attempt to use atomic direct IO. Atomic
905 writes are guaranteed to be stable once acknowledged by
906 the operating system. Only Linux supports O_ATOMIC right
907 now.
908
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909buffered=bool If value is true, use buffered io. This is the opposite
910 of the 'direct' option. Defaults to true.
71bfa161 911
f7fa2653 912offset=int Start io at the given offset in the file. The data before
71bfa161
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913 the given offset will not be touched. This effectively
914 caps the file size at real_size - offset.
915
214ac7e0 916offset_increment=int If this is provided, then the real offset becomes
69bdd6ba
JH
917 offset + offset_increment * thread_number, where the thread
918 number is a counter that starts at 0 and is incremented for
919 each sub-job (i.e. when numjobs option is specified). This
920 option is useful if there are several jobs which are intended
921 to operate on a file in parallel disjoint segments, with
922 even spacing between the starting points.
214ac7e0 923
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924number_ios=int Fio will normally perform IOs until it has exhausted the size
925 of the region set by size=, or if it exhaust the allocated
926 time (or hits an error condition). With this setting, the
927 range/size can be set independently of the number of IOs to
928 perform. When fio reaches this number, it will exit normally
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929 and report status. Note that this does not extend the amount
930 of IO that will be done, it will only stop fio if this
931 condition is met before other end-of-job criteria.
ddf24e42 932
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933fsync=int If writing to a file, issue a sync of the dirty data
934 for every number of blocks given. For example, if you give
935 32 as a parameter, fio will sync the file for every 32
936 writes issued. If fio is using non-buffered io, we may
937 not sync the file. The exception is the sg io engine, which
6c219763 938 synchronizes the disk cache anyway.
71bfa161 939
e76b1da4 940fdatasync=int Like fsync= but uses fdatasync() to only sync data and not
5f9099ea 941 metadata blocks.
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942 In FreeBSD and Windows there is no fdatasync(), this falls back
943 to using fsync()
5f9099ea 944
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945sync_file_range=str:val Use sync_file_range() for every 'val' number of
946 write operations. Fio will track range of writes that
947 have happened since the last sync_file_range() call. 'str'
948 can currently be one or more of:
949
950 wait_before SYNC_FILE_RANGE_WAIT_BEFORE
951 write SYNC_FILE_RANGE_WRITE
952 wait_after SYNC_FILE_RANGE_WAIT_AFTER
953
954 So if you do sync_file_range=wait_before,write:8, fio would
955 use SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE for
956 every 8 writes. Also see the sync_file_range(2) man page.
957 This option is Linux specific.
958
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959overwrite=bool If true, writes to a file will always overwrite existing
960 data. If the file doesn't already exist, it will be
961 created before the write phase begins. If the file exists
962 and is large enough for the specified write phase, nothing
963 will be done.
71bfa161 964
dbd11ead 965end_fsync=bool If true, fsync file contents when a write stage has completed.
71bfa161 966
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967fsync_on_close=bool If true, fio will fsync() a dirty file on close.
968 This differs from end_fsync in that it will happen on every
969 file close, not just at the end of the job.
970
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971rwmixread=int How large a percentage of the mix should be reads.
972
973rwmixwrite=int How large a percentage of the mix should be writes. If both
974 rwmixread and rwmixwrite is given and the values do not add
975 up to 100%, the latter of the two will be used to override
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976 the first. This may interfere with a given rate setting,
977 if fio is asked to limit reads or writes to a certain rate.
978 If that is the case, then the distribution may be skewed.
71bfa161 979
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980random_distribution=str:float By default, fio will use a completely uniform
981 random distribution when asked to perform random IO. Sometimes
982 it is useful to skew the distribution in specific ways,
983 ensuring that some parts of the data is more hot than others.
984 fio includes the following distribution models:
985
986 random Uniform random distribution
987 zipf Zipf distribution
988 pareto Pareto distribution
8116fd24 989 gauss Normal (guassian) distribution
e0a04ac1 990 zoned Zoned random distribution
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991
992 When using a zipf or pareto distribution, an input value
993 is also needed to define the access pattern. For zipf, this
994 is the zipf theta. For pareto, it's the pareto power. Fio
995 includes a test program, genzipf, that can be used visualize
996 what the given input values will yield in terms of hit rates.
997 If you wanted to use zipf with a theta of 1.2, you would use
998 random_distribution=zipf:1.2 as the option. If a non-uniform
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999 model is used, fio will disable use of the random map. For
1000 the gauss distribution, a normal deviation is supplied as
1001 a value between 0 and 100.
92d42d69 1002
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1003 For a zoned distribution, fio supports specifying percentages
1004 of IO access that should fall within what range of the file or
1005 device. For example, given a criteria of:
1006
1007 60% of accesses should be to the first 10%
1008 30% of accesses should be to the next 20%
1009 8% of accesses should be to to the next 30%
1010 2% of accesses should be to the next 40%
1011
1012 we can define that through zoning of the random accesses. For
1013 the above example, the user would do:
1014
1015 random_distribution=zoned:60/10:30/20:8/30:2/40
1016
1017 similarly to how bssplit works for setting ranges and
1018 percentages of block sizes. Like bssplit, it's possible to
1019 specify separate zones for reads, writes, and trims. If just
1020 one set is given, it'll apply to all of them.
1021
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1022percentage_random=int For a random workload, set how big a percentage should
1023 be random. This defaults to 100%, in which case the workload
1024 is fully random. It can be set from anywhere from 0 to 100.
1025 Setting it to 0 would make the workload fully sequential. Any
1026 setting in between will result in a random mix of sequential
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1027 and random IO, at the given percentages. It is possible to
1028 set different values for reads, writes, and trim. To do so,
1029 simply use a comma separated list. See blocksize.
211c9b89 1030
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1031norandommap Normally fio will cover every block of the file when doing
1032 random IO. If this option is given, fio will just get a
1033 new random offset without looking at past io history. This
1034 means that some blocks may not be read or written, and that
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1035 some blocks may be read/written more than once. If this option
1036 is used with verify= and multiple blocksizes (via bsrange=),
1037 only intact blocks are verified, i.e., partially-overwritten
1038 blocks are ignored.
bb8895e0 1039
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1040softrandommap=bool See norandommap. If fio runs with the random block map
1041 enabled and it fails to allocate the map, if this option is
1042 set it will continue without a random block map. As coverage
1043 will not be as complete as with random maps, this option is
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1044 disabled by default.
1045
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1046random_generator=str Fio supports the following engines for generating
1047 IO offsets for random IO:
1048
1049 tausworthe Strong 2^88 cycle random number generator
1050 lfsr Linear feedback shift register generator
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JA
1051 tausworthe64 Strong 64-bit 2^258 cycle random number
1052 generator
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JA
1053
1054 Tausworthe is a strong random number generator, but it
1055 requires tracking on the side if we want to ensure that
1056 blocks are only read or written once. LFSR guarantees
1057 that we never generate the same offset twice, and it's
1058 also less computationally expensive. It's not a true
1059 random generator, however, though for IO purposes it's
1060 typically good enough. LFSR only works with single
1061 block sizes, not with workloads that use multiple block
1062 sizes. If used with such a workload, fio may read or write
3bb85e84
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1063 some blocks multiple times. The default value is tausworthe,
1064 unless the required space exceeds 2^32 blocks. If it does,
1065 then tausworthe64 is selected automatically.
43f09da1 1066
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1067nice=int Run the job with the given nice value. See man nice(2).
1068
1069prio=int Set the io priority value of this job. Linux limits us to
1070 a positive value between 0 and 7, with 0 being the highest.
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1071 See man ionice(1). Refer to an appropriate manpage for
1072 other operating systems since meaning of priority may differ.
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1073
1074prioclass=int Set the io priority class. See man ionice(1).
1075
1076thinktime=int Stall the job x microseconds after an io has completed before
1077 issuing the next. May be used to simulate processing being
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1078 done by an application. See thinktime_blocks and
1079 thinktime_spin.
1080
1081thinktime_spin=int
1082 Only valid if thinktime is set - pretend to spend CPU time
1083 doing something with the data received, before falling back
1084 to sleeping for the rest of the period specified by
1085 thinktime.
9c1f7434 1086
4d01ece6 1087thinktime_blocks=int
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1088 Only valid if thinktime is set - control how many blocks
1089 to issue, before waiting 'thinktime' usecs. If not set,
1090 defaults to 1 which will make fio wait 'thinktime' usecs
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1091 after every block. This effectively makes any queue depth
1092 setting redundant, since no more than 1 IO will be queued
1093 before we have to complete it and do our thinktime. In
1094 other words, this setting effectively caps the queue depth
1095 if the latter is larger.
71bfa161 1096
581e7141 1097rate=int Cap the bandwidth used by this job. The number is in bytes/sec,
b09da8fa 1098 the normal suffix rules apply. You can use rate=500k to limit
581e7141
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1099 reads and writes to 500k each, or you can specify read and
1100 writes separately. Using rate=1m,500k would limit reads to
1101 1MB/sec and writes to 500KB/sec. Capping only reads or
1102 writes can be done with rate=,500k or rate=500k,. The former
1103 will only limit writes (to 500KB/sec), the latter will only
1104 limit reads.
71bfa161 1105
6d428bcd 1106rate_min=int Tell fio to do whatever it can to maintain at least this
4e991c23 1107 bandwidth. Failing to meet this requirement, will cause
581e7141
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1108 the job to exit. The same format as rate is used for
1109 read vs write separation.
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1110
1111rate_iops=int Cap the bandwidth to this number of IOPS. Basically the same
1112 as rate, just specified independently of bandwidth. If the
1113 job is given a block size range instead of a fixed value,
581e7141 1114 the smallest block size is used as the metric. The same format
de8f6de9 1115 as rate is used for read vs write separation.
4e991c23
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1116
1117rate_iops_min=int If fio doesn't meet this rate of IO, it will cause
581e7141 1118 the job to exit. The same format as rate is used for read vs
de8f6de9 1119 write separation.
71bfa161 1120
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1121rate_process=str This option controls how fio manages rated IO
1122 submissions. The default is 'linear', which submits IO in a
1123 linear fashion with fixed delays between IOs that gets
1124 adjusted based on IO completion rates. If this is set to
1125 'poisson', fio will submit IO based on a more real world
1126 random request flow, known as the Poisson process
5d02b083
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1127 (https://en.wikipedia.org/wiki/Poisson_process). The lambda
1128 will be 10^6 / IOPS for the given workload.
e7b24047 1129
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1130latency_target=int If set, fio will attempt to find the max performance
1131 point that the given workload will run at while maintaining a
1132 latency below this target. The values is given in microseconds.
1133 See latency_window and latency_percentile
1134
1135latency_window=int Used with latency_target to specify the sample window
1136 that the job is run at varying queue depths to test the
1137 performance. The value is given in microseconds.
1138
1139latency_percentile=float The percentage of IOs that must fall within the
1140 criteria specified by latency_target and latency_window. If not
1141 set, this defaults to 100.0, meaning that all IOs must be equal
1142 or below to the value set by latency_target.
1143
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1144max_latency=int If set, fio will exit the job if it exceeds this maximum
1145 latency. It will exit with an ETIME error.
1146
6d428bcd 1147rate_cycle=int Average bandwidth for 'rate' and 'rate_min' over this number
6c219763 1148 of milliseconds.
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1149
1150cpumask=int Set the CPU affinity of this job. The parameter given is a
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1151 bitmask of allowed CPU's the job may run on. So if you want
1152 the allowed CPUs to be 1 and 5, you would pass the decimal
1153 value of (1 << 1 | 1 << 5), or 34. See man
7dbb6eba 1154 sched_setaffinity(2). This may not work on all supported
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1155 operating systems or kernel versions. This option doesn't
1156 work well for a higher CPU count than what you can store in
1157 an integer mask, so it can only control cpus 1-32. For
1158 boxes with larger CPU counts, use cpus_allowed.
71bfa161 1159
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1160cpus_allowed=str Controls the same options as cpumask, but it allows a text
1161 setting of the permitted CPUs instead. So to use CPUs 1 and
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JA
1162 5, you would specify cpus_allowed=1,5. This options also
1163 allows a range of CPUs. Say you wanted a binding to CPUs
1164 1, 5, and 8-15, you would set cpus_allowed=1,5,8-15.
d2e268b0 1165
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JA
1166cpus_allowed_policy=str Set the policy of how fio distributes the CPUs
1167 specified by cpus_allowed or cpumask. Two policies are
1168 supported:
1169
1170 shared All jobs will share the CPU set specified.
1171 split Each job will get a unique CPU from the CPU set.
1172
1173 'shared' is the default behaviour, if the option isn't
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1174 specified. If split is specified, then fio will will assign
1175 one cpu per job. If not enough CPUs are given for the jobs
1176 listed, then fio will roundrobin the CPUs in the set.
c2acfbac 1177
769d13b5 1178numa_cpu_nodes=str Set this job running on specified NUMA nodes' CPUs. The
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YR
1179 arguments allow comma delimited list of cpu numbers,
1180 A-B ranges, or 'all'. Note, to enable numa options support,
67bf9823 1181 fio must be built on a system with libnuma-dev(el) installed.
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YR
1182
1183numa_mem_policy=str Set this job's memory policy and corresponding NUMA
1184 nodes. Format of the argements:
1185 <mode>[:<nodelist>]
1186 `mode' is one of the following memory policy:
1187 default, prefer, bind, interleave, local
1188 For `default' and `local' memory policy, no node is
1189 needed to be specified.
1190 For `prefer', only one node is allowed.
1191 For `bind' and `interleave', it allow comma delimited
1192 list of numbers, A-B ranges, or 'all'.
1193
e417fd66 1194startdelay=time Start this job the specified number of seconds after fio
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1195 has started. Only useful if the job file contains several
1196 jobs, and you want to delay starting some jobs to a certain
1197 time.
1198
e417fd66 1199runtime=time Tell fio to terminate processing after the specified number
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1200 of seconds. It can be quite hard to determine for how long
1201 a specified job will run, so this parameter is handy to
1202 cap the total runtime to a given time.
1203
cf4464ca 1204time_based If set, fio will run for the duration of the runtime
bf9a3edb 1205 specified even if the file(s) are completely read or
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JA
1206 written. It will simply loop over the same workload
1207 as many times as the runtime allows.
1208
e417fd66 1209ramp_time=time If set, fio will run the specified workload for this amount
721938ae
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1210 of time before logging any performance numbers. Useful for
1211 letting performance settle before logging results, thus
b29ee5b3
JA
1212 minimizing the runtime required for stable results. Note
1213 that the ramp_time is considered lead in time for a job,
1214 thus it will increase the total runtime if a special timeout
1215 or runtime is specified.
721938ae 1216
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1217invalidate=bool Invalidate the buffer/page cache parts for this file prior
1218 to starting io. Defaults to true.
1219
1220sync=bool Use sync io for buffered writes. For the majority of the
1221 io engines, this means using O_SYNC.
1222
d3aad8f2 1223iomem=str
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1224mem=str Fio can use various types of memory as the io unit buffer.
1225 The allowed values are:
1226
1227 malloc Use memory from malloc(3) as the buffers.
38f8c318 1228 Default memory type.
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1229
1230 shm Use shared memory as the buffers. Allocated
1231 through shmget(2).
1232
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1233 shmhuge Same as shm, but use huge pages as backing.
1234
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1235 mmap Use mmap to allocate buffers. May either be
1236 anonymous memory, or can be file backed if
1237 a filename is given after the option. The
1238 format is mem=mmap:/path/to/file.
71bfa161 1239
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1240 mmaphuge Use a memory mapped huge file as the buffer
1241 backing. Append filename after mmaphuge, ala
1242 mem=mmaphuge:/hugetlbfs/file
1243
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JA
1244 mmapshared Same as mmap, but use a MMAP_SHARED
1245 mapping.
1246
71bfa161 1247 The area allocated is a function of the maximum allowed
5394ae5f
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1248 bs size for the job, multiplied by the io depth given. Note
1249 that for shmhuge and mmaphuge to work, the system must have
1250 free huge pages allocated. This can normally be checked
1251 and set by reading/writing /proc/sys/vm/nr_hugepages on a
b22989b9 1252 Linux system. Fio assumes a huge page is 4MB in size. So
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JA
1253 to calculate the number of huge pages you need for a given
1254 job file, add up the io depth of all jobs (normally one unless
1255 iodepth= is used) and multiply by the maximum bs set. Then
1256 divide that number by the huge page size. You can see the
1257 size of the huge pages in /proc/meminfo. If no huge pages
1258 are allocated by having a non-zero number in nr_hugepages,
56bb17f2 1259 using mmaphuge or shmhuge will fail. Also see hugepage-size.
5394ae5f
JA
1260
1261 mmaphuge also needs to have hugetlbfs mounted and the file
1262 location should point there. So if it's mounted in /huge,
1263 you would use mem=mmaphuge:/huge/somefile.
71bfa161 1264
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1265iomem_align=int This indiciates the memory alignment of the IO memory buffers.
1266 Note that the given alignment is applied to the first IO unit
1267 buffer, if using iodepth the alignment of the following buffers
1268 are given by the bs used. In other words, if using a bs that is
1269 a multiple of the page sized in the system, all buffers will
1270 be aligned to this value. If using a bs that is not page
1271 aligned, the alignment of subsequent IO memory buffers is the
1272 sum of the iomem_align and bs used.
1273
f7fa2653 1274hugepage-size=int
56bb17f2 1275 Defines the size of a huge page. Must at least be equal
b22989b9 1276 to the system setting, see /proc/meminfo. Defaults to 4MB.
c51074e7
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1277 Should probably always be a multiple of megabytes, so using
1278 hugepage-size=Xm is the preferred way to set this to avoid
1279 setting a non-pow-2 bad value.
56bb17f2 1280
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1281exitall When one job finishes, terminate the rest. The default is
1282 to wait for each job to finish, sometimes that is not the
1283 desired action.
1284
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1285exitall_on_error When one job finishes in error, terminate the rest. The
1286 default is to wait for each job to finish.
1287
71bfa161 1288bwavgtime=int Average the calculated bandwidth over the given time. Value
a47591e4
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1289 is specified in milliseconds. If the job also does bandwidth
1290 logging through 'write_bw_log', then the minimum of this option
1291 and 'log_avg_msec' will be used. Default: 500ms.
71bfa161 1292
c8eeb9df 1293iopsavgtime=int Average the calculated IOPS over the given time. Value
a47591e4
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1294 is specified in milliseconds. If the job also does IOPS logging
1295 through 'write_iops_log', then the minimum of this option and
1296 'log_avg_msec' will be used. Default: 500ms.
c8eeb9df 1297
c2b8035f 1298create_serialize=bool If true, serialize the file creation for the jobs.
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1299 This may be handy to avoid interleaving of data
1300 files, which may greatly depend on the filesystem
1301 used and even the number of processors in the system.
1302
1303create_fsync=bool fsync the data file after creation. This is the
1304 default.
1305
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1306create_on_open=bool Don't pre-setup the files for IO, just create open()
1307 when it's time to do IO to that file.
1308
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1309create_only=bool If true, fio will only run the setup phase of the job.
1310 If files need to be laid out or updated on disk, only
1311 that will be done. The actual job contents are not
1312 executed.
1313
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1314allow_file_create=bool If true, fio is permitted to create files as part
1315 of its workload. This is the default behavior. If this
1316 option is false, then fio will error out if the files it
1317 needs to use don't already exist. Default: true.
1318
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1319allow_mounted_write=bool If this isn't set, fio will abort jobs that
1320 are destructive (eg that write) to what appears to be a
1321 mounted device or partition. This should help catch creating
1322 inadvertently destructive tests, not realizing that the test
1323 will destroy data on the mounted file system. Default: false.
1324
afad68f7 1325pre_read=bool If this is given, files will be pre-read into memory before
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JA
1326 starting the given IO operation. This will also clear
1327 the 'invalidate' flag, since it is pointless to pre-read
9c0d2241
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1328 and then drop the cache. This will only work for IO engines
1329 that are seekable, since they allow you to read the same data
1330 multiple times. Thus it will not work on eg network or splice
1331 IO.
afad68f7 1332
e545a6ce 1333unlink=bool Unlink the job files when done. Not the default, as repeated
bf9a3edb
JA
1334 runs of that job would then waste time recreating the file
1335 set again and again.
71bfa161 1336
39c1c323 1337unlink_each_loop=bool Unlink job files after each iteration or loop.
1338
71bfa161
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1339loops=int Run the specified number of iterations of this job. Used
1340 to repeat the same workload a given number of times. Defaults
1341 to 1.
1342
62167762
JC
1343verify_only Do not perform specified workload---only verify data still
1344 matches previous invocation of this workload. This option
1345 allows one to check data multiple times at a later date
1346 without overwriting it. This option makes sense only for
1347 workloads that write data, and does not support workloads
1348 with the time_based option set.
1349
68e1f29a 1350do_verify=bool Run the verify phase after a write phase. Only makes sense if
e84c73a8
SL
1351 verify is set. Defaults to 1.
1352
71bfa161 1353verify=str If writing to a file, fio can verify the file contents
b638d82f
RP
1354 after each iteration of the job. Each verification method also implies
1355 verification of special header, which is written to the beginning of
1356 each block. This header also includes meta information, like offset
1357 of the block, block number, timestamp when block was written, etc.
1358 verify=str can be combined with verify_pattern=str option.
1359 The allowed values are:
71bfa161
JA
1360
1361 md5 Use an md5 sum of the data area and store
1362 it in the header of each block.
1363
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1364 crc64 Use an experimental crc64 sum of the data
1365 area and store it in the header of each
1366 block.
1367
bac39e0e
JA
1368 crc32c Use a crc32c sum of the data area and store
1369 it in the header of each block.
1370
3845591f 1371 crc32c-intel Use hardware assisted crc32c calcuation
0539d758
JA
1372 provided on SSE4.2 enabled processors. Falls
1373 back to regular software crc32c, if not
1374 supported by the system.
3845591f 1375
71bfa161
JA
1376 crc32 Use a crc32 sum of the data area and store
1377 it in the header of each block.
1378
969f7ed3
JA
1379 crc16 Use a crc16 sum of the data area and store
1380 it in the header of each block.
1381
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JA
1382 crc7 Use a crc7 sum of the data area and store
1383 it in the header of each block.
1384
844ea602
JA
1385 xxhash Use xxhash as the checksum function. Generally
1386 the fastest software checksum that fio
1387 supports.
1388
cd14cc10
JA
1389 sha512 Use sha512 as the checksum function.
1390
1391 sha256 Use sha256 as the checksum function.
1392
7c353ceb
JA
1393 sha1 Use optimized sha1 as the checksum function.
1394
b638d82f
RP
1395 meta This option is deprecated, since now meta information is
1396 included in generic verification header and meta verification
1397 happens by default. For detailed information see the description
1398 of the verify=str setting. This option is kept because of
1399 compatibility's sake with old configurations. Do not use it.
7437ee87 1400
59245381
JA
1401 pattern Verify a strict pattern. Normally fio includes
1402 a header with some basic information and
1403 checksumming, but if this option is set, only
1404 the specific pattern set with 'verify_pattern'
1405 is verified.
1406
36690c9b
JA
1407 null Only pretend to verify. Useful for testing
1408 internals with ioengine=null, not for much
1409 else.
1410
6c219763 1411 This option can be used for repeated burn-in tests of a
71bfa161 1412 system to make sure that the written data is also
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JA
1413 correctly read back. If the data direction given is
1414 a read or random read, fio will assume that it should
1415 verify a previously written file. If the data direction
1416 includes any form of write, the verify will be of the
1417 newly written data.
71bfa161 1418
160b966d
JA
1419verifysort=bool If set, fio will sort written verify blocks when it deems
1420 it faster to read them back in a sorted manner. This is
1421 often the case when overwriting an existing file, since
1422 the blocks are already laid out in the file system. You
1423 can ignore this option unless doing huge amounts of really
1424 fast IO where the red-black tree sorting CPU time becomes
1425 significant.
3f9f4e26 1426
f7fa2653 1427verify_offset=int Swap the verification header with data somewhere else
546a9142
SL
1428 in the block before writing. Its swapped back before
1429 verifying.
1430
f7fa2653 1431verify_interval=int Write the verification header at a finer granularity
3f9f4e26
SL
1432 than the blocksize. It will be written for chunks the
1433 size of header_interval. blocksize should divide this
1434 evenly.
90059d65 1435
0e92f873 1436verify_pattern=str If set, fio will fill the io buffers with this
e28218f3
SL
1437 pattern. Fio defaults to filling with totally random
1438 bytes, but sometimes it's interesting to fill with a known
1439 pattern for io verification purposes. Depending on the
1440 width of the pattern, fio will fill 1/2/3/4 bytes of the
0e92f873
RR
1441 buffer at the time(it can be either a decimal or a hex number).
1442 The verify_pattern if larger than a 32-bit quantity has to
996093bb 1443 be a hex number that starts with either "0x" or "0X". Use
b638d82f 1444 with verify=str. Also, verify_pattern supports %o format,
61b9861d
RP
1445 which means that for each block offset will be written and
1446 then verifyied back, e.g.:
1447
1448 verify_pattern=%o
1449
1450 Or use combination of everything:
1451 verify_pattern=0xff%o"abcd"-12
e28218f3 1452
68e1f29a 1453verify_fatal=bool Normally fio will keep checking the entire contents
a12a3b4d
JA
1454 before quitting on a block verification failure. If this
1455 option is set, fio will exit the job on the first observed
1456 failure.
e8462bd8 1457
b463e936
JA
1458verify_dump=bool If set, dump the contents of both the original data
1459 block and the data block we read off disk to files. This
1460 allows later analysis to inspect just what kind of data
ef71e317 1461 corruption occurred. Off by default.
b463e936 1462
e8462bd8
JA
1463verify_async=int Fio will normally verify IO inline from the submitting
1464 thread. This option takes an integer describing how many
1465 async offload threads to create for IO verification instead,
1466 causing fio to offload the duty of verifying IO contents
c85c324c
JA
1467 to one or more separate threads. If using this offload
1468 option, even sync IO engines can benefit from using an
1469 iodepth setting higher than 1, as it allows them to have
1470 IO in flight while verifies are running.
e8462bd8
JA
1471
1472verify_async_cpus=str Tell fio to set the given CPU affinity on the
1473 async IO verification threads. See cpus_allowed for the
1474 format used.
6f87418f
JA
1475
1476verify_backlog=int Fio will normally verify the written contents of a
1477 job that utilizes verify once that job has completed. In
1478 other words, everything is written then everything is read
1479 back and verified. You may want to verify continually
1480 instead for a variety of reasons. Fio stores the meta data
1481 associated with an IO block in memory, so for large
1482 verify workloads, quite a bit of memory would be used up
1483 holding this meta data. If this option is enabled, fio
f42195a3
JA
1484 will write only N blocks before verifying these blocks.
1485
6f87418f
JA
1486verify_backlog_batch=int Control how many blocks fio will verify
1487 if verify_backlog is set. If not set, will default to
1488 the value of verify_backlog (meaning the entire queue
f42195a3
JA
1489 is read back and verified). If verify_backlog_batch is
1490 less than verify_backlog then not all blocks will be verified,
1491 if verify_backlog_batch is larger than verify_backlog, some
1492 blocks will be verified more than once.
66c098b8 1493
ca09be4b
JA
1494verify_state_save=bool When a job exits during the write phase of a verify
1495 workload, save its current state. This allows fio to replay
1496 up until that point, if the verify state is loaded for the
1497 verify read phase. The format of the filename is, roughly,
1498 <type>-<jobname>-<jobindex>-verify.state. <type> is "local"
1499 for a local run, "sock" for a client/server socket connection,
1500 and "ip" (192.168.0.1, for instance) for a networked
1501 client/server connection.
1502
1503verify_state_load=bool If a verify termination trigger was used, fio stores
1504 the current write state of each thread. This can be used at
1505 verification time so that fio knows how far it should verify.
1506 Without this information, fio will run a full verification
1507 pass, according to the settings in the job file used.
1508
d392365e 1509stonewall
de8f6de9 1510wait_for_previous Wait for preceding jobs in the job file to exit, before
71bfa161 1511 starting this one. Can be used to insert serialization
b3d62a75
JA
1512 points in the job file. A stone wall also implies starting
1513 a new reporting group.
1514
abcab6af 1515new_group Start a new reporting group. See: group_reporting.
71bfa161
JA
1516
1517numjobs=int Create the specified number of clones of this job. May be
1518 used to setup a larger number of threads/processes doing
abcab6af
AV
1519 the same thing. Each thread is reported separately; to see
1520 statistics for all clones as a whole, use group_reporting in
1521 conjunction with new_group.
1522
1523group_reporting It may sometimes be interesting to display statistics for
04b2f799
JA
1524 groups of jobs as a whole instead of for each individual job.
1525 This is especially true if 'numjobs' is used; looking at
1526 individual thread/process output quickly becomes unwieldy.
1527 To see the final report per-group instead of per-job, use
1528 'group_reporting'. Jobs in a file will be part of the same
1529 reporting group, unless if separated by a stonewall, or by
1530 using 'new_group'.
71bfa161
JA
1531
1532thread fio defaults to forking jobs, however if this option is
1533 given, fio will use pthread_create(3) to create threads
1534 instead.
1535
f7fa2653 1536zonesize=int Divide a file into zones of the specified size. See zoneskip.
71bfa161 1537
f7fa2653 1538zoneskip=int Skip the specified number of bytes when zonesize data has
71bfa161
JA
1539 been read. The two zone options can be used to only do
1540 io on zones of a file.
1541
076efc7c 1542write_iolog=str Write the issued io patterns to the specified file. See
5b42a488
SH
1543 read_iolog. Specify a separate file for each job, otherwise
1544 the iologs will be interspersed and the file may be corrupt.
71bfa161 1545
076efc7c 1546read_iolog=str Open an iolog with the specified file name and replay the
71bfa161 1547 io patterns it contains. This can be used to store a
6df8adaa
JA
1548 workload and replay it sometime later. The iolog given
1549 may also be a blktrace binary file, which allows fio
1550 to replay a workload captured by blktrace. See blktrace
1551 for how to capture such logging data. For blktrace replay,
1552 the file needs to be turned into a blkparse binary data
ea3e51c3 1553 file first (blkparse <device> -o /dev/null -d file_for_fio.bin).
66c098b8 1554
64bbb865 1555replay_no_stall=int When replaying I/O with read_iolog the default behavior
62776229
JA
1556 is to attempt to respect the time stamps within the log and
1557 replay them with the appropriate delay between IOPS. By
1558 setting this variable fio will not respect the timestamps and
1559 attempt to replay them as fast as possible while still
1560 respecting ordering. The result is the same I/O pattern to a
1561 given device, but different timings.
71bfa161 1562
d1c46c04
DN
1563replay_redirect=str While replaying I/O patterns using read_iolog the
1564 default behavior is to replay the IOPS onto the major/minor
1565 device that each IOP was recorded from. This is sometimes
de8f6de9 1566 undesirable because on a different machine those major/minor
d1c46c04
DN
1567 numbers can map to a different device. Changing hardware on
1568 the same system can also result in a different major/minor
1569 mapping. Replay_redirect causes all IOPS to be replayed onto
1570 the single specified device regardless of the device it was
1571 recorded from. i.e. replay_redirect=/dev/sdc would cause all
1572 IO in the blktrace to be replayed onto /dev/sdc. This means
1573 multiple devices will be replayed onto a single, if the trace
1574 contains multiple devices. If you want multiple devices to be
1575 replayed concurrently to multiple redirected devices you must
1576 blkparse your trace into separate traces and replay them with
1577 independent fio invocations. Unfortuantely this also breaks
1578 the strict time ordering between multiple device accesses.
1579
0c63576e
JA
1580replay_align=int Force alignment of IO offsets and lengths in a trace
1581 to this power of 2 value.
1582
1583replay_scale=int Scale sector offsets down by this factor when
1584 replaying traces.
1585
3a5db920
JA
1586per_job_logs=bool If set, this generates bw/clat/iops log with per
1587 file private filenames. If not set, jobs with identical names
1588 will share the log filename. Default: true.
1589
e3cedca7 1590write_bw_log=str If given, write a bandwidth log of the jobs in this job
71bfa161 1591 file. Can be used to store data of the bandwidth of the
e0da9bc2
JA
1592 jobs in their lifetime. The included fio_generate_plots
1593 script uses gnuplot to turn these text files into nice
ddb754db 1594 graphs. See write_lat_log for behaviour of given
8ad3b3dd
JA
1595 filename. For this option, the suffix is _bw.x.log, where
1596 x is the index of the job (1..N, where N is the number of
3a5db920 1597 jobs). If 'per_job_logs' is false, then the filename will not
a3ae5b05 1598 include the job index. See 'Log File Formats'.
71bfa161 1599
e3cedca7 1600write_lat_log=str Same as write_bw_log, except that this option stores io
02af0988
JA
1601 submission, completion, and total latencies instead. If no
1602 filename is given with this option, the default filename of
1603 "jobname_type.log" is used. Even if the filename is given,
1604 fio will still append the type of log. So if one specifies
e3cedca7
JA
1605
1606 write_lat_log=foo
1607
8ad3b3dd
JA
1608 The actual log names will be foo_slat.x.log, foo_clat.x.log,
1609 and foo_lat.x.log, where x is the index of the job (1..N,
1610 where N is the number of jobs). This helps fio_generate_plot
dd32be11 1611 find the logs automatically. If 'per_job_logs' is false, then
a3ae5b05
JA
1612 the filename will not include the job index. See 'Log File
1613 Formats'.
71bfa161 1614
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KC
1615write_hist_log=str Same as write_lat_log, but writes I/O completion
1616 latency histograms. If no filename is given with this option, the
1617 default filename of "jobname_clat_hist.x.log" is used, where x is
1618 the index of the job (1..N, where N is the number of jobs). Even
1619 if the filename is given, fio will still append the type of log.
1620 If per_job_logs is false, then the filename will not include the
1621 job index. See 'Log File Formats'.
1622
b8bc8cba
JA
1623write_iops_log=str Same as write_bw_log, but writes IOPS. If no filename is
1624 given with this option, the default filename of
8ad3b3dd
JA
1625 "jobname_type.x.log" is used,where x is the index of the job
1626 (1..N, where N is the number of jobs). Even if the filename
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JA
1627 is given, fio will still append the type of log. If
1628 'per_job_logs' is false, then the filename will not include
a3ae5b05 1629 the job index. See 'Log File Formats'.
b8bc8cba
JA
1630
1631log_avg_msec=int By default, fio will log an entry in the iops, latency,
1632 or bw log for every IO that completes. When writing to the
1633 disk log, that can quickly grow to a very large size. Setting
1634 this option makes fio average the each log entry over the
1635 specified period of time, reducing the resolution of the log.
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JA
1636 See log_max_value as well. Defaults to 0, logging all entries.
1637
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KC
1638log_hist_msec=int Same as log_avg_msec, but logs entries for completion
1639 latency histograms. Computing latency percentiles from averages of
1640 intervals using log_avg_msec is innacurate. Setting this option makes
1641 fio log histogram entries over the specified period of time, reducing
1642 log sizes for high IOPS devices while retaining percentile accuracy.
1643 See log_hist_coarseness as well. Defaults to 0, meaning histogram
1644 logging is disabled.
1645
1646log_hist_coarseness=int Integer ranging from 0 to 6, defining the coarseness
1647 of the resolution of the histogram logs enabled with log_hist_msec. For
1648 each increment in coarseness, fio outputs half as many bins. Defaults to
1649 0, for which histogram logs contain 1216 latency bins. See
1650 'Log File Formats'.
1651
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JA
1652log_max_value=bool If log_avg_msec is set, fio logs the average over that
1653 window. If you instead want to log the maximum value, set this
1654 option to 1. Defaults to 0, meaning that averaged values are
1655 logged.
b8bc8cba 1656
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JA
1657log_offset=int If this is set, the iolog options will include the byte
1658 offset for the IO entry as well as the other data values.
1659
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JA
1660log_compression=int If this is set, fio will compress the IO logs as
1661 it goes, to keep the memory footprint lower. When a log
1662 reaches the specified size, that chunk is removed and
1663 compressed in the background. Given that IO logs are
1664 fairly highly compressible, this yields a nice memory
1665 savings for longer runs. The downside is that the
1666 compression will consume some background CPU cycles, so
1667 it may impact the run. This, however, is also true if
1668 the logging ends up consuming most of the system memory.
1669 So pick your poison. The IO logs are saved normally at the
1670 end of a run, by decompressing the chunks and storing them
1671 in the specified log file. This feature depends on the
1672 availability of zlib.
1673
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JA
1674log_compression_cpus=str Define the set of CPUs that are allowed to
1675 handle online log compression for the IO jobs. This can
1676 provide better isolation between performance sensitive jobs,
1677 and background compression work.
1678
1679log_store_compressed=bool If set, fio will store the log files in a
1680 compressed format. They can be decompressed with fio, using
1681 the --inflate-log command line parameter. The files will be
1682 stored with a .fz suffix.
b26317c9 1683
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1684log_unix_epoch=bool If set, fio will log Unix timestamps to the log
1685 files produced by enabling write_type_log for each log type, instead
1686 of the default zero-based timestamps.
1687
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DE
1688block_error_percentiles=bool If set, record errors in trim block-sized
1689 units from writes and trims and output a histogram of
1690 how many trims it took to get to errors, and what kind
1691 of error was encountered.
1692
f7fa2653 1693lockmem=int Pin down the specified amount of memory with mlock(2). Can
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1694 potentially be used instead of removing memory or booting
1695 with less memory to simulate a smaller amount of memory.
81c6b6cd 1696 The amount specified is per worker.
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1697
1698exec_prerun=str Before running this job, issue the command specified
74c8c488
JA
1699 through system(3). Output is redirected in a file called
1700 jobname.prerun.txt.
71bfa161
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1701
1702exec_postrun=str After the job completes, issue the command specified
74c8c488
JA
1703 though system(3). Output is redirected in a file called
1704 jobname.postrun.txt.
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1705
1706ioscheduler=str Attempt to switch the device hosting the file to the specified
1707 io scheduler before running.
1708
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1709disk_util=bool Generate disk utilization statistics, if the platform
1710 supports it. Defaults to on.
1711
02af0988 1712disable_lat=bool Disable measurements of total latency numbers. Useful
9520ebb9
JA
1713 only for cutting back the number of calls to gettimeofday,
1714 as that does impact performance at really high IOPS rates.
1715 Note that to really get rid of a large amount of these
1716 calls, this option must be used with disable_slat and
1717 disable_bw as well.
1718
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JA
1719disable_clat=bool Disable measurements of completion latency numbers. See
1720 disable_lat.
1721
9520ebb9 1722disable_slat=bool Disable measurements of submission latency numbers. See
02af0988 1723 disable_slat.
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JA
1724
1725disable_bw=bool Disable measurements of throughput/bandwidth numbers. See
02af0988 1726 disable_lat.
9520ebb9 1727
83349190
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1728clat_percentiles=bool Enable the reporting of percentiles of
1729 completion latencies.
1730
1731percentile_list=float_list Overwrite the default list of percentiles
66347cfa
DE
1732 for completion latencies and the block error histogram.
1733 Each number is a floating number in the range (0,100],
1734 and the maximum length of the list is 20. Use ':'
1735 to separate the numbers, and list the numbers in ascending
1736 order. For example, --percentile_list=99.5:99.9 will cause
1737 fio to report the values of completion latency below which
1738 99.5% and 99.9% of the observed latencies fell, respectively.
83349190 1739
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1740clocksource=str Use the given clocksource as the base of timing. The
1741 supported options are:
1742
1743 gettimeofday gettimeofday(2)
1744
1745 clock_gettime clock_gettime(2)
1746
1747 cpu Internal CPU clock source
1748
1749 cpu is the preferred clocksource if it is reliable, as it
1750 is very fast (and fio is heavy on time calls). Fio will
1751 automatically use this clocksource if it's supported and
1752 considered reliable on the system it is running on, unless
1753 another clocksource is specifically set. For x86/x86-64 CPUs,
1754 this means supporting TSC Invariant.
1755
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JA
1756gtod_reduce=bool Enable all of the gettimeofday() reducing options
1757 (disable_clat, disable_slat, disable_bw) plus reduce
1758 precision of the timeout somewhat to really shrink
1759 the gettimeofday() call count. With this option enabled,
1760 we only do about 0.4% of the gtod() calls we would have
1761 done if all time keeping was enabled.
1762
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1763gtod_cpu=int Sometimes it's cheaper to dedicate a single thread of
1764 execution to just getting the current time. Fio (and
1765 databases, for instance) are very intensive on gettimeofday()
1766 calls. With this option, you can set one CPU aside for
1767 doing nothing but logging current time to a shared memory
1768 location. Then the other threads/processes that run IO
1769 workloads need only copy that segment, instead of entering
1770 the kernel with a gettimeofday() call. The CPU set aside
1771 for doing these time calls will be excluded from other
1772 uses. Fio will manually clear it from the CPU mask of other
1773 jobs.
a696fa2a 1774
06842027 1775continue_on_error=str Normally fio will exit the job on the first observed
f2bba182
RR
1776 failure. If this option is set, fio will continue the job when
1777 there is a 'non-fatal error' (EIO or EILSEQ) until the runtime
1778 is exceeded or the I/O size specified is completed. If this
1779 option is used, there are two more stats that are appended,
1780 the total error count and the first error. The error field
1781 given in the stats is the first error that was hit during the
1782 run.
be4ecfdf 1783
06842027
SL
1784 The allowed values are:
1785
1786 none Exit on any IO or verify errors.
1787
1788 read Continue on read errors, exit on all others.
1789
1790 write Continue on write errors, exit on all others.
1791
1792 io Continue on any IO error, exit on all others.
1793
1794 verify Continue on verify errors, exit on all others.
1795
1796 all Continue on all errors.
1797
1798 0 Backward-compatible alias for 'none'.
1799
1800 1 Backward-compatible alias for 'all'.
1801
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1802ignore_error=str Sometimes you want to ignore some errors during test
1803 in that case you can specify error list for each error type.
1804 ignore_error=READ_ERR_LIST,WRITE_ERR_LIST,VERIFY_ERR_LIST
1805 errors for given error type is separated with ':'. Error
1806 may be symbol ('ENOSPC', 'ENOMEM') or integer.
1807 Example:
1808 ignore_error=EAGAIN,ENOSPC:122
66c098b8
BC
1809 This option will ignore EAGAIN from READ, and ENOSPC and
1810 122(EDQUOT) from WRITE.
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1811
1812error_dump=bool If set dump every error even if it is non fatal, true
1813 by default. If disabled only fatal error will be dumped
66c098b8 1814
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JA
1815cgroup=str Add job to this control group. If it doesn't exist, it will
1816 be created. The system must have a mounted cgroup blkio
1817 mount point for this to work. If your system doesn't have it
1818 mounted, you can do so with:
a696fa2a
JA
1819
1820 # mount -t cgroup -o blkio none /cgroup
1821
a696fa2a
JA
1822cgroup_weight=int Set the weight of the cgroup to this value. See
1823 the documentation that comes with the kernel, allowed values
1824 are in the range of 100..1000.
71bfa161 1825
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VG
1826cgroup_nodelete=bool Normally fio will delete the cgroups it has created after
1827 the job completion. To override this behavior and to leave
1828 cgroups around after the job completion, set cgroup_nodelete=1.
1829 This can be useful if one wants to inspect various cgroup
1830 files after job completion. Default: false
1831
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JA
1832uid=int Instead of running as the invoking user, set the user ID to
1833 this value before the thread/process does any work.
1834
1835gid=int Set group ID, see uid.
1836
9e684a49
DE
1837flow_id=int The ID of the flow. If not specified, it defaults to being a
1838 global flow. See flow.
1839
1840flow=int Weight in token-based flow control. If this value is used, then
1841 there is a 'flow counter' which is used to regulate the
1842 proportion of activity between two or more jobs. fio attempts
1843 to keep this flow counter near zero. The 'flow' parameter
1844 stands for how much should be added or subtracted to the flow
1845 counter on each iteration of the main I/O loop. That is, if
1846 one job has flow=8 and another job has flow=-1, then there
1847 will be a roughly 1:8 ratio in how much one runs vs the other.
1848
1849flow_watermark=int The maximum value that the absolute value of the flow
1850 counter is allowed to reach before the job must wait for a
1851 lower value of the counter.
1852
1853flow_sleep=int The period of time, in microseconds, to wait after the flow
1854 watermark has been exceeded before retrying operations
1855
de890a1e
SL
1856In addition, there are some parameters which are only valid when a specific
1857ioengine is in use. These are used identically to normal parameters, with the
1858caveat that when used on the command line, they must come after the ioengine
1859that defines them is selected.
1860
1861[libaio] userspace_reap Normally, with the libaio engine in use, fio will use
1862 the io_getevents system call to reap newly returned events.
1863 With this flag turned on, the AIO ring will be read directly
1864 from user-space to reap events. The reaping mode is only
1865 enabled when polling for a minimum of 0 events (eg when
1866 iodepth_batch_complete=0).
1867
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1868[psyncv2] hipri Set RWF_HIPRI on IO, indicating to the kernel that
1869 it's of higher priority than normal.
1870
2403767a 1871[cpuio] cpuload=int Attempt to use the specified percentage of CPU cycles.
0353050f 1872
2403767a 1873[cpuio] cpuchunks=int Split the load into cycles of the given time. In
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1874 microseconds.
1875
2403767a 1876[cpuio] exit_on_io_done=bool Detect when IO threads are done, then exit.
046395d7 1877
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SL
1878[netsplice] hostname=str
1879[net] hostname=str The host name or IP address to use for TCP or UDP based IO.
1880 If the job is a TCP listener or UDP reader, the hostname is not
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SB
1881 used and must be omitted unless it is a valid UDP multicast
1882 address.
a3f001f5 1883[libhdfs] namenode=str The host name or IP address of a HDFS cluster namenode to contact.
de890a1e
SL
1884
1885[netsplice] port=int
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JA
1886[net] port=int The TCP or UDP port to bind to or connect to. If this is used
1887with numjobs to spawn multiple instances of the same job type, then this will
1888be the starting port number since fio will use a range of ports.
a3f001f5 1889[libhdfs] port=int the listening port of the HFDS cluster namenode.
de890a1e 1890
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SB
1891[netsplice] interface=str
1892[net] interface=str The IP address of the network interface used to send or
1893 receive UDP multicast
1894
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SB
1895[netsplice] ttl=int
1896[net] ttl=int Time-to-live value for outgoing UDP multicast packets.
1897 Default: 1
1898
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1899[netsplice] nodelay=bool
1900[net] nodelay=bool Set TCP_NODELAY on TCP connections.
1901
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SL
1902[netsplice] protocol=str
1903[netsplice] proto=str
1904[net] protocol=str
1905[net] proto=str The network protocol to use. Accepted values are:
1906
1907 tcp Transmission control protocol
49ccb8c1 1908 tcpv6 Transmission control protocol V6
f5cc3d0e 1909 udp User datagram protocol
49ccb8c1 1910 udpv6 User datagram protocol V6
de890a1e
SL
1911 unix UNIX domain socket
1912
1913 When the protocol is TCP or UDP, the port must also be given,
1914 as well as the hostname if the job is a TCP listener or UDP
1915 reader. For unix sockets, the normal filename option should be
1916 used and the port is invalid.
1917
1918[net] listen For TCP network connections, tell fio to listen for incoming
1919 connections rather than initiating an outgoing connection. The
1920 hostname must be omitted if this option is used.
1008602c 1921
b511c9aa 1922[net] pingpong Normaly a network writer will just continue writing data, and
7aeb1e94
JA
1923 a network reader will just consume packages. If pingpong=1
1924 is set, a writer will send its normal payload to the reader,
1925 then wait for the reader to send the same payload back. This
1926 allows fio to measure network latencies. The submission
1927 and completion latencies then measure local time spent
1928 sending or receiving, and the completion latency measures
1929 how long it took for the other end to receive and send back.
b511c9aa
SB
1930 For UDP multicast traffic pingpong=1 should only be set for a
1931 single reader when multiple readers are listening to the same
1932 address.
7aeb1e94 1933
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1934[net] window_size Set the desired socket buffer size for the connection.
1935
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1936[net] mss Set the TCP maximum segment size (TCP_MAXSEG).
1937
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1938[e4defrag] donorname=str
1939 File will be used as a block donor(swap extents between files)
1940[e4defrag] inplace=int
66c098b8 1941 Configure donor file blocks allocation strategy
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1942 0(default): Preallocate donor's file on init
1943 1 : allocate space immidietly inside defragment event,
1944 and free right after event
1945
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1946[rbd] clustername=str Specifies the name of the Ceph cluster.
1947[rbd] rbdname=str Specifies the name of the RBD.
1948[rbd] pool=str Specifies the naem of the Ceph pool containing RBD.
1949[rbd] clientname=str Specifies the username (without the 'client.' prefix)
1950 used to access the Ceph cluster. If the clustername is
1951 specified, the clientmae shall be the full type.id
1952 string. If no type. prefix is given, fio will add
1953 'client.' by default.
1954
65fa28ca 1955[mtd] skip_bad=bool Skip operations against known bad blocks.
de890a1e 1956
a3f001f5 1957[libhdfs] hdfsdirectory libhdfs will create chunk in this HDFS directory
dda13f44 1958[libhdfs] chunk_size the size of the chunk to use for each file.
a3f001f5 1959
de890a1e 1960
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19616.0 Interpreting the output
1962---------------------------
1963
1964fio spits out a lot of output. While running, fio will display the
1965status of the jobs created. An example of that would be:
1966
73c8b082 1967Threads: 1: [_r] [24.8% done] [ 13509/ 8334 kb/s] [eta 00h:01m:31s]
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1968
1969The characters inside the square brackets denote the current status of
1970each thread. The possible values (in typical life cycle order) are:
1971
1972Idle Run
1973---- ---
1974P Thread setup, but not started.
1975C Thread created.
9c6f6316 1976I Thread initialized, waiting or generating necessary data.
b0f65863 1977 p Thread running pre-reading file(s).
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1978 R Running, doing sequential reads.
1979 r Running, doing random reads.
1980 W Running, doing sequential writes.
1981 w Running, doing random writes.
1982 M Running, doing mixed sequential reads/writes.
1983 m Running, doing mixed random reads/writes.
1984 F Running, currently waiting for fsync()
3d434057 1985 f Running, finishing up (writing IO logs, etc)
fc6bd43c 1986 V Running, doing verification of written data.
71bfa161 1987E Thread exited, not reaped by main thread yet.
4f7e57a4
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1988_ Thread reaped, or
1989X Thread reaped, exited with an error.
a5e371a6 1990K Thread reaped, exited due to signal.
71bfa161 1991
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1992Fio will condense the thread string as not to take up more space on the
1993command line as is needed. For instance, if you have 10 readers and 10
1994writers running, the output would look like this:
1995
1996Jobs: 20 (f=20): [R(10),W(10)] [4.0% done] [2103MB/0KB/0KB /s] [538K/0/0 iops] [eta 57m:36s]
1997
1998Fio will still maintain the ordering, though. So the above means that jobs
19991..10 are readers, and 11..20 are writers.
2000
71bfa161 2001The other values are fairly self explanatory - number of threads
c9f60304
JA
2002currently running and doing io, rate of io since last check (read speed
2003listed first, then write speed), and the estimated completion percentage
2004and time for the running group. It's impossible to estimate runtime of
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JA
2005the following groups (if any). Note that the string is displayed in order,
2006so it's possible to tell which of the jobs are currently doing what. The
2007first character is the first job defined in the job file, and so forth.
71bfa161
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2008
2009When fio is done (or interrupted by ctrl-c), it will show the data for
2010each thread, group of threads, and disks in that order. For each data
2011direction, the output looks like:
2012
2013Client1 (g=0): err= 0:
35649e58 2014 write: io= 32MB, bw= 666KB/s, iops=89 , runt= 50320msec
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JA
2015 slat (msec): min= 0, max= 136, avg= 0.03, stdev= 1.92
2016 clat (msec): min= 0, max= 631, avg=48.50, stdev=86.82
b22989b9 2017 bw (KB/s) : min= 0, max= 1196, per=51.00%, avg=664.02, stdev=681.68
e7823a94 2018 cpu : usr=1.49%, sys=0.25%, ctx=7969, majf=0, minf=17
71619dc2 2019 IO depths : 1=0.1%, 2=0.3%, 4=0.5%, 8=99.0%, 16=0.0%, 32=0.0%, >32=0.0%
838bc709
JA
2020 submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
2021 complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
30061b97 2022 issued r/w: total=0/32768, short=0/0
8abdce66
JA
2023 lat (msec): 2=1.6%, 4=0.0%, 10=3.2%, 20=12.8%, 50=38.4%, 100=24.8%,
2024 lat (msec): 250=15.2%, 500=0.0%, 750=0.0%, 1000=0.0%, >=2048=0.0%
71bfa161
JA
2025
2026The client number is printed, along with the group id and error of that
2027thread. Below is the io statistics, here for writes. In the order listed,
2028they denote:
2029
2030io= Number of megabytes io performed
2031bw= Average bandwidth rate
35649e58 2032iops= Average IOs performed per second
71bfa161 2033runt= The runtime of that thread
72fbda2a 2034 slat= Submission latency (avg being the average, stdev being the
71bfa161
JA
2035 standard deviation). This is the time it took to submit
2036 the io. For sync io, the slat is really the completion
8a35c71e 2037 latency, since queue/complete is one operation there. This
bf9a3edb 2038 value can be in milliseconds or microseconds, fio will choose
8a35c71e 2039 the most appropriate base and print that. In the example
0d237712
LAG
2040 above, milliseconds is the best scale. Note: in --minimal mode
2041 latencies are always expressed in microseconds.
71bfa161
JA
2042 clat= Completion latency. Same names as slat, this denotes the
2043 time from submission to completion of the io pieces. For
2044 sync io, clat will usually be equal (or very close) to 0,
2045 as the time from submit to complete is basically just
2046 CPU time (io has already been done, see slat explanation).
2047 bw= Bandwidth. Same names as the xlat stats, but also includes
2048 an approximate percentage of total aggregate bandwidth
2049 this thread received in this group. This last value is
2050 only really useful if the threads in this group are on the
2051 same disk, since they are then competing for disk access.
2052cpu= CPU usage. User and system time, along with the number
e7823a94
JA
2053 of context switches this thread went through, usage of
2054 system and user time, and finally the number of major
23a8e176
JA
2055 and minor page faults. The CPU utilization numbers are
2056 averages for the jobs in that reporting group, while the
2057 context and fault counters are summed.
71619dc2
JA
2058IO depths= The distribution of io depths over the job life time. The
2059 numbers are divided into powers of 2, so for example the
2060 16= entries includes depths up to that value but higher
2061 than the previous entry. In other words, it covers the
2062 range from 16 to 31.
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JA
2063IO submit= How many pieces of IO were submitting in a single submit
2064 call. Each entry denotes that amount and below, until
2065 the previous entry - eg, 8=100% mean that we submitted
2066 anywhere in between 5-8 ios per submit call.
2067IO complete= Like the above submit number, but for completions instead.
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JA
2068IO issued= The number of read/write requests issued, and how many
2069 of them were short.
ec118304
JA
2070IO latencies= The distribution of IO completion latencies. This is the
2071 time from when IO leaves fio and when it gets completed.
2072 The numbers follow the same pattern as the IO depths,
2073 meaning that 2=1.6% means that 1.6% of the IO completed
8abdce66
JA
2074 within 2 msecs, 20=12.8% means that 12.8% of the IO
2075 took more than 10 msecs, but less than (or equal to) 20 msecs.
71bfa161
JA
2076
2077After each client has been listed, the group statistics are printed. They
2078will look like this:
2079
2080Run status group 0 (all jobs):
b22989b9
JA
2081 READ: io=64MB, aggrb=22178, minb=11355, maxb=11814, mint=2840msec, maxt=2955msec
2082 WRITE: io=64MB, aggrb=1302, minb=666, maxb=669, mint=50093msec, maxt=50320msec
71bfa161
JA
2083
2084For each data direction, it prints:
2085
2086io= Number of megabytes io performed.
2087aggrb= Aggregate bandwidth of threads in this group.
2088minb= The minimum average bandwidth a thread saw.
2089maxb= The maximum average bandwidth a thread saw.
2090mint= The smallest runtime of the threads in that group.
2091maxt= The longest runtime of the threads in that group.
2092
2093And finally, the disk statistics are printed. They will look like this:
2094
2095Disk stats (read/write):
2096 sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00%
2097
2098Each value is printed for both reads and writes, with reads first. The
2099numbers denote:
2100
2101ios= Number of ios performed by all groups.
2102merge= Number of merges io the io scheduler.
2103ticks= Number of ticks we kept the disk busy.
2104io_queue= Total time spent in the disk queue.
2105util= The disk utilization. A value of 100% means we kept the disk
2106 busy constantly, 50% would be a disk idling half of the time.
2107
8423bd11
JA
2108It is also possible to get fio to dump the current output while it is
2109running, without terminating the job. To do that, send fio the USR1 signal.
06464907
JA
2110You can also get regularly timed dumps by using the --status-interval
2111parameter, or by creating a file in /tmp named fio-dump-status. If fio
2112sees this file, it will unlink it and dump the current output status.
8423bd11 2113
71bfa161
JA
2114
21157.0 Terse output
2116----------------
2117
2118For scripted usage where you typically want to generate tables or graphs
6af019c9 2119of the results, fio can output the results in a semicolon separated format.
71bfa161
JA
2120The format is one long line of values, such as:
2121
562c2d2f
DN
21222;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%
2123A description of this job goes here.
2124
2125The job description (if provided) follows on a second line.
71bfa161 2126
525c2bfa
JA
2127To enable terse output, use the --minimal command line option. The first
2128value is the version of the terse output format. If the output has to
2129be changed for some reason, this number will be incremented by 1 to
2130signify that change.
6820cb3b 2131
71bfa161
JA
2132Split up, the format is as follows:
2133
5e726d0a 2134 terse version, fio version, jobname, groupid, error
71bfa161 2135 READ status:
312b4af2 2136 Total IO (KB), bandwidth (KB/sec), IOPS, runtime (msec)
d86ae56c
CW
2137 Submission latency: min, max, mean, stdev (usec)
2138 Completion latency: min, max, mean, stdev (usec)
1db92cb6 2139 Completion latency percentiles: 20 fields (see below)
d86ae56c
CW
2140 Total latency: min, max, mean, stdev (usec)
2141 Bw (KB/s): min, max, aggregate percentage of total, mean, stdev
71bfa161 2142 WRITE status:
312b4af2 2143 Total IO (KB), bandwidth (KB/sec), IOPS, runtime (msec)
d86ae56c
CW
2144 Submission latency: min, max, mean, stdev (usec)
2145 Completion latency: min, max, mean, stdev(usec)
1db92cb6 2146 Completion latency percentiles: 20 fields (see below)
d86ae56c
CW
2147 Total latency: min, max, mean, stdev (usec)
2148 Bw (KB/s): min, max, aggregate percentage of total, mean, stdev
046ee302 2149 CPU usage: user, system, context switches, major faults, minor faults
2270890c 2150 IO depths: <=1, 2, 4, 8, 16, 32, >=64
562c2d2f
DN
2151 IO latencies microseconds: <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000
2152 IO latencies milliseconds: <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, 2000, >=2000
f2f788dd
JA
2153 Disk utilization: Disk name, Read ios, write ios,
2154 Read merges, write merges,
2155 Read ticks, write ticks,
3d7cd9b4 2156 Time spent in queue, disk utilization percentage
de8f6de9 2157 Additional Info (dependent on continue_on_error, default off): total # errors, first error code
66c098b8 2158
de8f6de9 2159 Additional Info (dependent on description being set): Text description
25c8b9d7 2160
1db92cb6
JA
2161Completion latency percentiles can be a grouping of up to 20 sets, so
2162for the terse output fio writes all of them. Each field will look like this:
2163
2164 1.00%=6112
2165
2166which is the Xth percentile, and the usec latency associated with it.
2167
f2f788dd
JA
2168For disk utilization, all disks used by fio are shown. So for each disk
2169there will be a disk utilization section.
2170
25c8b9d7
PD
2171
21728.0 Trace file format
2173---------------------
66c098b8 2174There are two trace file format that you can encounter. The older (v1) format
25c8b9d7
PD
2175is unsupported since version 1.20-rc3 (March 2008). It will still be described
2176below in case that you get an old trace and want to understand it.
2177
2178In any case the trace is a simple text file with a single action per line.
2179
2180
21818.1 Trace file format v1
2182------------------------
2183Each line represents a single io action in the following format:
2184
2185rw, offset, length
2186
2187where rw=0/1 for read/write, and the offset and length entries being in bytes.
2188
2189This format is not supported in Fio versions => 1.20-rc3.
2190
2191
21928.2 Trace file format v2
2193------------------------
2194The second version of the trace file format was added in Fio version 1.17.
2195It allows to access more then one file per trace and has a bigger set of
2196possible file actions.
2197
2198The first line of the trace file has to be:
2199
2200fio version 2 iolog
2201
2202Following this can be lines in two different formats, which are described below.
2203
2204The file management format:
2205
2206filename action
2207
2208The filename is given as an absolute path. The action can be one of these:
2209
2210add Add the given filename to the trace
66c098b8 2211open Open the file with the given filename. The filename has to have
25c8b9d7
PD
2212 been added with the add action before.
2213close Close the file with the given filename. The file has to have been
2214 opened before.
2215
2216
2217The file io action format:
2218
2219filename action offset length
2220
2221The filename is given as an absolute path, and has to have been added and opened
66c098b8 2222before it can be used with this format. The offset and length are given in
25c8b9d7
PD
2223bytes. The action can be one of these:
2224
2225wait Wait for 'offset' microseconds. Everything below 100 is discarded.
5c7808fe 2226 The time is relative to the previous wait statement.
25c8b9d7
PD
2227read Read 'length' bytes beginning from 'offset'
2228write Write 'length' bytes beginning from 'offset'
2229sync fsync() the file
2230datasync fdatasync() the file
2231trim trim the given file from the given 'offset' for 'length' bytes
f2a2ce0e
HL
2232
2233
22349.0 CPU idleness profiling
06464907 2235--------------------------
f2a2ce0e
HL
2236In some cases, we want to understand CPU overhead in a test. For example,
2237we test patches for the specific goodness of whether they reduce CPU usage.
2238fio implements a balloon approach to create a thread per CPU that runs at
2239idle priority, meaning that it only runs when nobody else needs the cpu.
2240By measuring the amount of work completed by the thread, idleness of each
2241CPU can be derived accordingly.
2242
2243An unit work is defined as touching a full page of unsigned characters. Mean
2244and standard deviation of time to complete an unit work is reported in "unit
2245work" section. Options can be chosen to report detailed percpu idleness or
2246overall system idleness by aggregating percpu stats.
99b9a85a
JA
2247
2248
224910.0 Verification and triggers
2250------------------------------
2251Fio is usually run in one of two ways, when data verification is done. The
2252first is a normal write job of some sort with verify enabled. When the
2253write phase has completed, fio switches to reads and verifies everything
2254it wrote. The second model is running just the write phase, and then later
2255on running the same job (but with reads instead of writes) to repeat the
2256same IO patterns and verify the contents. Both of these methods depend
2257on the write phase being completed, as fio otherwise has no idea how much
2258data was written.
2259
2260With verification triggers, fio supports dumping the current write state
2261to local files. Then a subsequent read verify workload can load this state
2262and know exactly where to stop. This is useful for testing cases where
2263power is cut to a server in a managed fashion, for instance.
2264
2265A verification trigger consists of two things:
2266
22671) Storing the write state of each job
22682) Executing a trigger command
2269
2270The write state is relatively small, on the order of hundreds of bytes
2271to single kilobytes. It contains information on the number of completions
2272done, the last X completions, etc.
2273
2274A trigger is invoked either through creation ('touch') of a specified
2275file in the system, or through a timeout setting. If fio is run with
2276--trigger-file=/tmp/trigger-file, then it will continually check for
2277the existence of /tmp/trigger-file. When it sees this file, it will
2278fire off the trigger (thus saving state, and executing the trigger
2279command).
2280
2281For client/server runs, there's both a local and remote trigger. If
2282fio is running as a server backend, it will send the job states back
2283to the client for safe storage, then execute the remote trigger, if
2284specified. If a local trigger is specified, the server will still send
2285back the write state, but the client will then execute the trigger.
2286
228710.1 Verification trigger example
2288---------------------------------
2289Lets say we want to run a powercut test on the remote machine 'server'.
2290Our write workload is in write-test.fio. We want to cut power to 'server'
2291at some point during the run, and we'll run this test from the safety
2292or our local machine, 'localbox'. On the server, we'll start the fio
2293backend normally:
2294
2295server# fio --server
2296
2297and on the client, we'll fire off the workload:
2298
2299localbox$ fio --client=server --trigger-file=/tmp/my-trigger --trigger-remote="bash -c \"echo b > /proc/sysrq-triger\""
2300
2301We set /tmp/my-trigger as the trigger file, and we tell fio to execute
2302
2303echo b > /proc/sysrq-trigger
2304
2305on the server once it has received the trigger and sent us the write
2306state. This will work, but it's not _really_ cutting power to the server,
2307it's merely abruptly rebooting it. If we have a remote way of cutting
2308power to the server through IPMI or similar, we could do that through
2309a local trigger command instead. Lets assume we have a script that does
2310IPMI reboot of a given hostname, ipmi-reboot. On localbox, we could
2311then have run fio with a local trigger instead:
2312
2313localbox$ fio --client=server --trigger-file=/tmp/my-trigger --trigger="ipmi-reboot server"
2314
2315For this case, fio would wait for the server to send us the write state,
2316then execute 'ipmi-reboot server' when that happened.
2317
29dbd1e5 231810.2 Loading verify state
99b9a85a
JA
2319-------------------------
2320To load store write state, read verification job file must contain
2321the verify_state_load option. If that is set, fio will load the previously
2322stored state. For a local fio run this is done by loading the files directly,
2323and on a client/server run, the server backend will ask the client to send
2324the files over and load them from there.
a3ae5b05
JA
2325
2326
232711.0 Log File Formats
2328---------------------
2329
2330Fio supports a variety of log file formats, for logging latencies, bandwidth,
2331and IOPS. The logs share a common format, which looks like this:
2332
2333time (msec), value, data direction, offset
2334
2335Time for the log entry is always in milliseconds. The value logged depends
2336on the type of log, it will be one of the following:
2337
2338 Latency log Value is latency in usecs
2339 Bandwidth log Value is in KB/sec
2340 IOPS log Value is IOPS
2341
2342Data direction is one of the following:
2343
2344 0 IO is a READ
2345 1 IO is a WRITE
2346 2 IO is a TRIM
2347
2348The offset is the offset, in bytes, from the start of the file, for that
2349particular IO. The logging of the offset can be toggled with 'log_offset'.
2350
2351If windowed logging is enabled though 'log_avg_msec', then fio doesn't log
2352individual IOs. Instead of logs the average values over the specified
2353period of time. Since 'data direction' and 'offset' are per-IO values,
2354they aren't applicable if windowed logging is enabled. If windowed logging
2355is enabled and 'log_max_value' is set, then fio logs maximum values in
2356that window instead of averages.
2357