8 5. Detailed list of parameters
13 1.0 Overview and history
14 ------------------------
15 fio was originally written to save me the hassle of writing special test
16 case programs when I wanted to test a specific workload, either for
17 performance reasons or to find/reproduce a bug. The process of writing
18 such a test app can be tiresome, especially if you have to do it often.
19 Hence I needed a tool that would be able to simulate a given io workload
20 without resorting to writing a tailored test case again and again.
22 A test work load is difficult to define, though. There can be any number
23 of processes or threads involved, and they can each be using their own
24 way of generating io. You could have someone dirtying large amounts of
25 memory in an memory mapped file, or maybe several threads issuing
26 reads using asynchronous io. fio needed to be flexible enough to
27 simulate both of these cases, and many more.
31 The first step in getting fio to simulate a desired io workload, is
32 writing a job file describing that specific setup. A job file may contain
33 any number of threads and/or files - the typical contents of the job file
34 is a global section defining shared parameters, and one or more job
35 sections describing the jobs involved. When run, fio parses this file
36 and sets everything up as described. If we break down a job from top to
37 bottom, it contains the following basic parameters:
39 IO type Defines the io pattern issued to the file(s).
40 We may only be reading sequentially from this
41 file(s), or we may be writing randomly. Or even
42 mixing reads and writes, sequentially or randomly.
44 Block size In how large chunks are we issuing io? This may be
45 a single value, or it may describe a range of
48 IO size How much data are we going to be reading/writing.
50 IO engine How do we issue io? We could be memory mapping the
51 file, we could be using regular read/write, we
52 could be using splice, async io, syslet, or even
55 IO depth If the io engine is async, how large a queuing
56 depth do we want to maintain?
58 IO type Should we be doing buffered io, or direct/raw io?
60 Num files How many files are we spreading the workload over.
62 Num threads How many threads or processes should we spread
65 The above are the basic parameters defined for a workload, in addition
66 there's a multitude of parameters that modify other aspects of how this
72 See the README file for command line parameters, there are only a few
75 Running fio is normally the easiest part - you just give it the job file
76 (or job files) as parameters:
80 and it will start doing what the job_file tells it to do. You can give
81 more than one job file on the command line, fio will serialize the running
82 of those files. Internally that is the same as using the 'stonewall'
83 parameter described the the parameter section.
85 If the job file contains only one job, you may as well just give the
86 parameters on the command line. The command line parameters are identical
87 to the job parameters, with a few extra that control global parameters
88 (see README). For example, for the job file parameter iodepth=2, the
89 mirror command line option would be --iodepth 2 or --iodepth=2. You can
90 also use the command line for giving more than one job entry. For each
91 --name option that fio sees, it will start a new job with that name.
92 Command line entries following a --name entry will apply to that job,
93 until there are no more entries or a new --name entry is seen. This is
94 similar to the job file options, where each option applies to the current
95 job until a new [] job entry is seen.
97 fio does not need to run as root, except if the files or devices specified
98 in the job section requires that. Some other options may also be restricted,
99 such as memory locking, io scheduler switching, and decreasing the nice value.
104 As previously described, fio accepts one or more job files describing
105 what it is supposed to do. The job file format is the classic ini file,
106 where the names enclosed in [] brackets define the job name. You are free
107 to use any ascii name you want, except 'global' which has special meaning.
108 A global section sets defaults for the jobs described in that file. A job
109 may override a global section parameter, and a job file may even have
110 several global sections if so desired. A job is only affected by a global
111 section residing above it. If the first character in a line is a ';' or a
112 '#', the entire line is discarded as a comment.
114 So let's look at a really simple job file that defines two processes, each
115 randomly reading from a 128MB file.
117 ; -- start job file --
128 As you can see, the job file sections themselves are empty as all the
129 described parameters are shared. As no filename= option is given, fio
130 makes up a filename for each of the jobs as it sees fit. On the command
131 line, this job would look as follows:
133 $ fio --name=global --rw=randread --size=128m --name=job1 --name=job2
136 Let's look at an example that has a number of processes writing randomly
139 ; -- start job file --
151 Here we have no global section, as we only have one job defined anyway.
152 We want to use async io here, with a depth of 4 for each file. We also
153 increased the buffer size used to 32KB and define numjobs to 4 to
154 fork 4 identical jobs. The result is 4 processes each randomly writing
155 to their own 64MB file. Instead of using the above job file, you could
156 have given the parameters on the command line. For this case, you would
159 $ fio --name=random-writers --ioengine=libaio --iodepth=4 --rw=randwrite --bs=32k --direct=0 --size=64m --numjobs=4
161 4.1 Environment variables
162 -------------------------
164 fio also supports environment variable expansion in job files. Any
165 substring of the form "${VARNAME}" as part of an option value (in other
166 words, on the right of the `='), will be expanded to the value of the
167 environment variable called VARNAME. If no such environment variable
168 is defined, or VARNAME is the empty string, the empty string will be
171 As an example, let's look at a sample fio invocation and job file:
173 $ SIZE=64m NUMJOBS=4 fio jobfile.fio
175 ; -- start job file --
182 This will expand to the following equivalent job file at runtime:
184 ; -- start job file --
191 fio ships with a few example job files, you can also look there for
194 4.2 Reserved keywords
195 ---------------------
197 Additionally, fio has a set of reserved keywords that will be replaced
198 internally with the appropriate value. Those keywords are:
200 $pagesize The architecture page size of the running system
201 $mb_memory Megabytes of total memory in the system
202 $ncpus Number of online available CPUs
204 These can be used on the command line or in the job file, and will be
205 automatically substituted with the current system values when the job
206 is run. Simple math is also supported on these keywords, so you can
207 perform actions like:
211 and get that properly expanded to 8 times the size of memory in the
215 5.0 Detailed list of parameters
216 -------------------------------
218 This section describes in details each parameter associated with a job.
219 Some parameters take an option of a given type, such as an integer or
220 a string. The following types are used:
222 str String. This is a sequence of alpha characters.
223 time Integer with possible time suffix. In seconds unless otherwise
224 specified, use eg 10m for 10 minutes. Accepts s/m/h for seconds,
226 int SI integer. A whole number value, which may contain a suffix
227 describing the base of the number. Accepted suffixes are k/m/g/t/p,
228 meaning kilo, mega, giga, tera, and peta. The suffix is not case
229 sensitive, and you may also include trailing 'b' (eg 'kb' is the same
230 as 'k'). So if you want to specify 4096, you could either write
231 out '4096' or just give 4k. The suffixes signify base 2 values, so
232 1024 is 1k and 1024k is 1m and so on, unless the suffix is explicitly
233 set to a base 10 value using 'kib', 'mib', 'gib', etc. If that is the
234 case, then 1000 is used as the multiplier. This can be handy for
235 disks, since manufacturers generally use base 10 values when listing
236 the capacity of a drive. If the option accepts an upper and lower
237 range, use a colon ':' or minus '-' to separate such values. May also
238 include a prefix to indicate numbers base. If 0x is used, the number
239 is assumed to be hexadecimal. See irange.
240 bool Boolean. Usually parsed as an integer, however only defined for
241 true and false (1 and 0).
242 irange Integer range with suffix. Allows value range to be given, such
243 as 1024-4096. A colon may also be used as the separator, eg
244 1k:4k. If the option allows two sets of ranges, they can be
245 specified with a ',' or '/' delimiter: 1k-4k/8k-32k. Also see
247 float_list A list of floating numbers, separated by a ':' character.
249 With the above in mind, here follows the complete list of fio job
252 name=str ASCII name of the job. This may be used to override the
253 name printed by fio for this job. Otherwise the job
254 name is used. On the command line this parameter has the
255 special purpose of also signaling the start of a new
258 description=str Text description of the job. Doesn't do anything except
259 dump this text description when this job is run. It's
262 directory=str Prefix filenames with this directory. Used to place files
263 in a different location than "./".
265 filename=str Fio normally makes up a filename based on the job name,
266 thread number, and file number. If you want to share
267 files between threads in a job or several jobs, specify
268 a filename for each of them to override the default. If
269 the ioengine used is 'net', the filename is the host, port,
270 and protocol to use in the format of =host,port,protocol.
271 See ioengine=net for more. If the ioengine is file based, you
272 can specify a number of files by separating the names with a
273 ':' colon. So if you wanted a job to open /dev/sda and /dev/sdb
274 as the two working files, you would use
275 filename=/dev/sda:/dev/sdb. On Windows, disk devices are accessed
276 as \\.\PhysicalDrive0 for the first device, \\.\PhysicalDrive1
277 for the second etc. If the wanted filename does need to
278 include a colon, then escape that with a '\' character.
279 For instance, if the filename is "/dev/dsk/foo@3,0:c",
280 then you would use filename="/dev/dsk/foo@3,0\:c".
281 '-' is a reserved name, meaning stdin or stdout. Which of the
282 two depends on the read/write direction set.
284 opendir=str Tell fio to recursively add any file it can find in this
285 directory and down the file system tree.
287 lockfile=str Fio defaults to not locking any files before it does
288 IO to them. If a file or file descriptor is shared, fio
289 can serialize IO to that file to make the end result
290 consistent. This is usual for emulating real workloads that
291 share files. The lock modes are:
293 none No locking. The default.
294 exclusive Only one thread/process may do IO,
295 excluding all others.
296 readwrite Read-write locking on the file. Many
297 readers may access the file at the
298 same time, but writes get exclusive
301 The option may be post-fixed with a lock batch number. If
302 set, then each thread/process may do that amount of IOs to
303 the file before giving up the lock. Since lock acquisition is
304 expensive, batching the lock/unlocks will speed up IO.
307 rw=str Type of io pattern. Accepted values are:
309 read Sequential reads
310 write Sequential writes
311 randwrite Random writes
312 randread Random reads
313 rw Sequential mixed reads and writes
314 randrw Random mixed reads and writes
316 For the mixed io types, the default is to split them 50/50.
317 For certain types of io the result may still be skewed a bit,
318 since the speed may be different. It is possible to specify
319 a number of IO's to do before getting a new offset, this is
320 one by appending a ':<nr>' to the end of the string given.
321 For a random read, it would look like 'rw=randread:8' for
322 passing in an offset modifier with a value of 8. If the
323 postfix is used with a sequential IO pattern, then the value
324 specified will be added to the generated offset for each IO.
325 For instance, using rw=write:4k will skip 4k for every
326 write. It turns sequential IO into sequential IO with holes.
327 See the 'rw_sequencer' option.
329 rw_sequencer=str If an offset modifier is given by appending a number to
330 the rw=<str> line, then this option controls how that
331 number modifies the IO offset being generated. Accepted
334 sequential Generate sequential offset
335 identical Generate the same offset
337 'sequential' is only useful for random IO, where fio would
338 normally generate a new random offset for every IO. If you
339 append eg 8 to randread, you would get a new random offset for
340 every 8 IO's. The result would be a seek for only every 8
341 IO's, instead of for every IO. Use rw=randread:8 to specify
342 that. As sequential IO is already sequential, setting
343 'sequential' for that would not result in any differences.
344 'identical' behaves in a similar fashion, except it sends
345 the same offset 8 number of times before generating a new
348 kb_base=int The base unit for a kilobyte. The defacto base is 2^10, 1024.
349 Storage manufacturers like to use 10^3 or 1000 as a base
350 ten unit instead, for obvious reasons. Allow values are
351 1024 or 1000, with 1024 being the default.
353 randrepeat=bool For random IO workloads, seed the generator in a predictable
354 way so that results are repeatable across repetitions.
356 use_os_rand=bool Fio can either use the random generator supplied by the OS
357 to generator random offsets, or it can use it's own internal
358 generator (based on Tausworthe). Default is to use the
359 internal generator, which is often of better quality and
362 fallocate=str Whether pre-allocation is performed when laying down files.
365 none Do not pre-allocate space
366 posix Pre-allocate via posix_fallocate()
367 keep Pre-allocate via fallocate() with
368 FALLOC_FL_KEEP_SIZE set
369 0 Backward-compatible alias for 'none'
370 1 Backward-compatible alias for 'posix'
372 May not be available on all supported platforms. 'keep' is only
373 available on Linux.If using ZFS on Solaris this must be set to
374 'none' because ZFS doesn't support it. Default: 'posix'.
376 fadvise_hint=bool By default, fio will use fadvise() to advise the kernel
377 on what IO patterns it is likely to issue. Sometimes you
378 want to test specific IO patterns without telling the
379 kernel about it, in which case you can disable this option.
380 If set, fio will use POSIX_FADV_SEQUENTIAL for sequential
381 IO and POSIX_FADV_RANDOM for random IO.
383 size=int The total size of file io for this job. Fio will run until
384 this many bytes has been transferred, unless runtime is
385 limited by other options (such as 'runtime', for instance).
386 Unless specific nrfiles and filesize options are given,
387 fio will divide this size between the available files
388 specified by the job. If not set, fio will use the full
389 size of the given files or devices. If the the files
390 do not exist, size must be given. It is also possible to
391 give size as a percentage between 1 and 100. If size=20%
392 is given, fio will use 20% of the full size of the given
395 filesize=int Individual file sizes. May be a range, in which case fio
396 will select sizes for files at random within the given range
397 and limited to 'size' in total (if that is given). If not
398 given, each created file is the same size.
401 fill_fs=bool Sets size to something really large and waits for ENOSPC (no
402 space left on device) as the terminating condition. Only makes
403 sense with sequential write. For a read workload, the mount
404 point will be filled first then IO started on the result. This
405 option doesn't make sense if operating on a raw device node,
406 since the size of that is already known by the file system.
407 Additionally, writing beyond end-of-device will not return
411 bs=int The block size used for the io units. Defaults to 4k. Values
412 can be given for both read and writes. If a single int is
413 given, it will apply to both. If a second int is specified
414 after a comma, it will apply to writes only. In other words,
415 the format is either bs=read_and_write or bs=read,write.
416 bs=4k,8k will thus use 4k blocks for reads, and 8k blocks
417 for writes. If you only wish to set the write size, you
418 can do so by passing an empty read size - bs=,8k will set
419 8k for writes and leave the read default value.
422 ba=int At what boundary to align random IO offsets. Defaults to
423 the same as 'blocksize' the minimum blocksize given.
424 Minimum alignment is typically 512b for using direct IO,
425 though it usually depends on the hardware block size. This
426 option is mutually exclusive with using a random map for
427 files, so it will turn off that option.
429 blocksize_range=irange
430 bsrange=irange Instead of giving a single block size, specify a range
431 and fio will mix the issued io block sizes. The issued
432 io unit will always be a multiple of the minimum value
433 given (also see bs_unaligned). Applies to both reads and
434 writes, however a second range can be given after a comma.
437 bssplit=str Sometimes you want even finer grained control of the
438 block sizes issued, not just an even split between them.
439 This option allows you to weight various block sizes,
440 so that you are able to define a specific amount of
441 block sizes issued. The format for this option is:
443 bssplit=blocksize/percentage:blocksize/percentage
445 for as many block sizes as needed. So if you want to define
446 a workload that has 50% 64k blocks, 10% 4k blocks, and
447 40% 32k blocks, you would write:
449 bssplit=4k/10:64k/50:32k/40
451 Ordering does not matter. If the percentage is left blank,
452 fio will fill in the remaining values evenly. So a bssplit
453 option like this one:
455 bssplit=4k/50:1k/:32k/
457 would have 50% 4k ios, and 25% 1k and 32k ios. The percentages
458 always add up to 100, if bssplit is given a range that adds
459 up to more, it will error out.
461 bssplit also supports giving separate splits to reads and
462 writes. The format is identical to what bs= accepts. You
463 have to separate the read and write parts with a comma. So
464 if you want a workload that has 50% 2k reads and 50% 4k reads,
465 while having 90% 4k writes and 10% 8k writes, you would
468 bssplit=2k/50:4k/50,4k/90,8k/10
471 bs_unaligned If this option is given, any byte size value within bsrange
472 may be used as a block range. This typically wont work with
473 direct IO, as that normally requires sector alignment.
475 zero_buffers If this option is given, fio will init the IO buffers to
476 all zeroes. The default is to fill them with random data.
478 refill_buffers If this option is given, fio will refill the IO buffers
479 on every submit. The default is to only fill it at init
480 time and reuse that data. Only makes sense if zero_buffers
481 isn't specified, naturally. If data verification is enabled,
482 refill_buffers is also automatically enabled.
484 scramble_buffers=bool If refill_buffers is too costly and the target is
485 using data deduplication, then setting this option will
486 slightly modify the IO buffer contents to defeat normal
487 de-dupe attempts. This is not enough to defeat more clever
488 block compression attempts, but it will stop naive dedupe of
489 blocks. Default: true.
491 nrfiles=int Number of files to use for this job. Defaults to 1.
493 openfiles=int Number of files to keep open at the same time. Defaults to
494 the same as nrfiles, can be set smaller to limit the number
497 file_service_type=str Defines how fio decides which file from a job to
498 service next. The following types are defined:
500 random Just choose a file at random.
502 roundrobin Round robin over open files. This
505 sequential Finish one file before moving on to
506 the next. Multiple files can still be
507 open depending on 'openfiles'.
509 The string can have a number appended, indicating how
510 often to switch to a new file. So if option random:4 is
511 given, fio will switch to a new random file after 4 ios
514 ioengine=str Defines how the job issues io to the file. The following
517 sync Basic read(2) or write(2) io. lseek(2) is
518 used to position the io location.
520 psync Basic pread(2) or pwrite(2) io.
522 vsync Basic readv(2) or writev(2) IO.
524 libaio Linux native asynchronous io. Note that Linux
525 may only support queued behaviour with
526 non-buffered IO (set direct=1 or buffered=0).
527 This engine defines engine specific options.
529 posixaio glibc posix asynchronous io.
531 solarisaio Solaris native asynchronous io.
533 windowsaio Windows native asynchronous io.
535 mmap File is memory mapped and data copied
536 to/from using memcpy(3).
538 splice splice(2) is used to transfer the data and
539 vmsplice(2) to transfer data from user
542 syslet-rw Use the syslet system calls to make
543 regular read/write async.
545 sg SCSI generic sg v3 io. May either be
546 synchronous using the SG_IO ioctl, or if
547 the target is an sg character device
548 we use read(2) and write(2) for asynchronous
551 null Doesn't transfer any data, just pretends
552 to. This is mainly used to exercise fio
553 itself and for debugging/testing purposes.
555 net Transfer over the network to given host:port.
556 Depending on the protocol used, the hostname,
557 port, listen and filename options are used to
558 specify what sort of connection to make, while
559 the protocol option determines which protocol
561 This engine defines engine specific options.
563 netsplice Like net, but uses splice/vmsplice to
564 map data and send/receive.
565 This engine defines engine specific options.
567 cpuio Doesn't transfer any data, but burns CPU
568 cycles according to the cpuload= and
569 cpucycle= options. Setting cpuload=85
570 will cause that job to do nothing but burn
571 85% of the CPU. In case of SMP machines,
572 use numjobs=<no_of_cpu> to get desired CPU
573 usage, as the cpuload only loads a single
574 CPU at the desired rate.
576 guasi The GUASI IO engine is the Generic Userspace
577 Asyncronous Syscall Interface approach
580 http://www.xmailserver.org/guasi-lib.html
582 for more info on GUASI.
584 rdma The RDMA I/O engine supports both RDMA
585 memory semantics (RDMA_WRITE/RDMA_READ) and
586 channel semantics (Send/Recv) for the
587 InfiniBand, RoCE and iWARP protocols.
589 external Prefix to specify loading an external
590 IO engine object file. Append the engine
591 filename, eg ioengine=external:/tmp/foo.o
592 to load ioengine foo.o in /tmp.
594 iodepth=int This defines how many io units to keep in flight against
595 the file. The default is 1 for each file defined in this
596 job, can be overridden with a larger value for higher
597 concurrency. Note that increasing iodepth beyond 1 will not
598 affect synchronous ioengines (except for small degress when
599 verify_async is in use). Even async engines may impose OS
600 restrictions causing the desired depth not to be achieved.
601 This may happen on Linux when using libaio and not setting
602 direct=1, since buffered IO is not async on that OS. Keep an
603 eye on the IO depth distribution in the fio output to verify
604 that the achieved depth is as expected. Default: 1.
606 iodepth_batch_submit=int
607 iodepth_batch=int This defines how many pieces of IO to submit at once.
608 It defaults to 1 which means that we submit each IO
609 as soon as it is available, but can be raised to submit
610 bigger batches of IO at the time.
612 iodepth_batch_complete=int This defines how many pieces of IO to retrieve
613 at once. It defaults to 1 which means that we'll ask
614 for a minimum of 1 IO in the retrieval process from
615 the kernel. The IO retrieval will go on until we
616 hit the limit set by iodepth_low. If this variable is
617 set to 0, then fio will always check for completed
618 events before queuing more IO. This helps reduce
619 IO latency, at the cost of more retrieval system calls.
621 iodepth_low=int The low water mark indicating when to start filling
622 the queue again. Defaults to the same as iodepth, meaning
623 that fio will attempt to keep the queue full at all times.
624 If iodepth is set to eg 16 and iodepth_low is set to 4, then
625 after fio has filled the queue of 16 requests, it will let
626 the depth drain down to 4 before starting to fill it again.
628 direct=bool If value is true, use non-buffered io. This is usually
629 O_DIRECT. Note that ZFS on Solaris doesn't support direct io.
630 On Windows the synchronous ioengines don't support direct io.
632 buffered=bool If value is true, use buffered io. This is the opposite
633 of the 'direct' option. Defaults to true.
635 offset=int Start io at the given offset in the file. The data before
636 the given offset will not be touched. This effectively
637 caps the file size at real_size - offset.
639 offset_increment=int If this is provided, then the real offset becomes
640 the offset + offset_increment * thread_number, where the
641 thread number is a counter that starts at 0 and is incremented
642 for each job. This option is useful if there are several jobs
643 which are intended to operate on a file in parallel in disjoint
644 segments, with even spacing between the starting points.
646 fsync=int If writing to a file, issue a sync of the dirty data
647 for every number of blocks given. For example, if you give
648 32 as a parameter, fio will sync the file for every 32
649 writes issued. If fio is using non-buffered io, we may
650 not sync the file. The exception is the sg io engine, which
651 synchronizes the disk cache anyway.
653 fdatasync=int Like fsync= but uses fdatasync() to only sync data and not
655 In FreeBSD and Windows there is no fdatasync(), this falls back to
658 sync_file_range=str:val Use sync_file_range() for every 'val' number of
659 write operations. Fio will track range of writes that
660 have happened since the last sync_file_range() call. 'str'
661 can currently be one or more of:
663 wait_before SYNC_FILE_RANGE_WAIT_BEFORE
664 write SYNC_FILE_RANGE_WRITE
665 wait_after SYNC_FILE_RANGE_WAIT_AFTER
667 So if you do sync_file_range=wait_before,write:8, fio would
668 use SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE for
669 every 8 writes. Also see the sync_file_range(2) man page.
670 This option is Linux specific.
672 overwrite=bool If true, writes to a file will always overwrite existing
673 data. If the file doesn't already exist, it will be
674 created before the write phase begins. If the file exists
675 and is large enough for the specified write phase, nothing
678 end_fsync=bool If true, fsync file contents when the job exits.
680 fsync_on_close=bool If true, fio will fsync() a dirty file on close.
681 This differs from end_fsync in that it will happen on every
682 file close, not just at the end of the job.
684 rwmixread=int How large a percentage of the mix should be reads.
686 rwmixwrite=int How large a percentage of the mix should be writes. If both
687 rwmixread and rwmixwrite is given and the values do not add
688 up to 100%, the latter of the two will be used to override
689 the first. This may interfere with a given rate setting,
690 if fio is asked to limit reads or writes to a certain rate.
691 If that is the case, then the distribution may be skewed.
693 norandommap Normally fio will cover every block of the file when doing
694 random IO. If this option is given, fio will just get a
695 new random offset without looking at past io history. This
696 means that some blocks may not be read or written, and that
697 some blocks may be read/written more than once. This option
698 is mutually exclusive with verify= if and only if multiple
699 blocksizes (via bsrange=) are used, since fio only tracks
700 complete rewrites of blocks.
702 softrandommap=bool See norandommap. If fio runs with the random block map
703 enabled and it fails to allocate the map, if this option is
704 set it will continue without a random block map. As coverage
705 will not be as complete as with random maps, this option is
708 nice=int Run the job with the given nice value. See man nice(2).
710 prio=int Set the io priority value of this job. Linux limits us to
711 a positive value between 0 and 7, with 0 being the highest.
714 prioclass=int Set the io priority class. See man ionice(1).
716 thinktime=int Stall the job x microseconds after an io has completed before
717 issuing the next. May be used to simulate processing being
718 done by an application. See thinktime_blocks and
722 Only valid if thinktime is set - pretend to spend CPU time
723 doing something with the data received, before falling back
724 to sleeping for the rest of the period specified by
728 Only valid if thinktime is set - control how many blocks
729 to issue, before waiting 'thinktime' usecs. If not set,
730 defaults to 1 which will make fio wait 'thinktime' usecs
733 rate=int Cap the bandwidth used by this job. The number is in bytes/sec,
734 the normal suffix rules apply. You can use rate=500k to limit
735 reads and writes to 500k each, or you can specify read and
736 writes separately. Using rate=1m,500k would limit reads to
737 1MB/sec and writes to 500KB/sec. Capping only reads or
738 writes can be done with rate=,500k or rate=500k,. The former
739 will only limit writes (to 500KB/sec), the latter will only
742 ratemin=int Tell fio to do whatever it can to maintain at least this
743 bandwidth. Failing to meet this requirement, will cause
744 the job to exit. The same format as rate is used for
745 read vs write separation.
747 rate_iops=int Cap the bandwidth to this number of IOPS. Basically the same
748 as rate, just specified independently of bandwidth. If the
749 job is given a block size range instead of a fixed value,
750 the smallest block size is used as the metric. The same format
751 as rate is used for read vs write seperation.
753 rate_iops_min=int If fio doesn't meet this rate of IO, it will cause
754 the job to exit. The same format as rate is used for read vs
757 ratecycle=int Average bandwidth for 'rate' and 'ratemin' over this number
760 cpumask=int Set the CPU affinity of this job. The parameter given is a
761 bitmask of allowed CPU's the job may run on. So if you want
762 the allowed CPUs to be 1 and 5, you would pass the decimal
763 value of (1 << 1 | 1 << 5), or 34. See man
764 sched_setaffinity(2). This may not work on all supported
765 operating systems or kernel versions. This option doesn't
766 work well for a higher CPU count than what you can store in
767 an integer mask, so it can only control cpus 1-32. For
768 boxes with larger CPU counts, use cpus_allowed.
770 cpus_allowed=str Controls the same options as cpumask, but it allows a text
771 setting of the permitted CPUs instead. So to use CPUs 1 and
772 5, you would specify cpus_allowed=1,5. This options also
773 allows a range of CPUs. Say you wanted a binding to CPUs
774 1, 5, and 8-15, you would set cpus_allowed=1,5,8-15.
776 startdelay=time Start this job the specified number of seconds after fio
777 has started. Only useful if the job file contains several
778 jobs, and you want to delay starting some jobs to a certain
781 runtime=time Tell fio to terminate processing after the specified number
782 of seconds. It can be quite hard to determine for how long
783 a specified job will run, so this parameter is handy to
784 cap the total runtime to a given time.
786 time_based If set, fio will run for the duration of the runtime
787 specified even if the file(s) are completely read or
788 written. It will simply loop over the same workload
789 as many times as the runtime allows.
791 ramp_time=time If set, fio will run the specified workload for this amount
792 of time before logging any performance numbers. Useful for
793 letting performance settle before logging results, thus
794 minimizing the runtime required for stable results. Note
795 that the ramp_time is considered lead in time for a job,
796 thus it will increase the total runtime if a special timeout
797 or runtime is specified.
799 invalidate=bool Invalidate the buffer/page cache parts for this file prior
800 to starting io. Defaults to true.
802 sync=bool Use sync io for buffered writes. For the majority of the
803 io engines, this means using O_SYNC.
806 mem=str Fio can use various types of memory as the io unit buffer.
807 The allowed values are:
809 malloc Use memory from malloc(3) as the buffers.
811 shm Use shared memory as the buffers. Allocated
814 shmhuge Same as shm, but use huge pages as backing.
816 mmap Use mmap to allocate buffers. May either be
817 anonymous memory, or can be file backed if
818 a filename is given after the option. The
819 format is mem=mmap:/path/to/file.
821 mmaphuge Use a memory mapped huge file as the buffer
822 backing. Append filename after mmaphuge, ala
823 mem=mmaphuge:/hugetlbfs/file
825 The area allocated is a function of the maximum allowed
826 bs size for the job, multiplied by the io depth given. Note
827 that for shmhuge and mmaphuge to work, the system must have
828 free huge pages allocated. This can normally be checked
829 and set by reading/writing /proc/sys/vm/nr_hugepages on a
830 Linux system. Fio assumes a huge page is 4MB in size. So
831 to calculate the number of huge pages you need for a given
832 job file, add up the io depth of all jobs (normally one unless
833 iodepth= is used) and multiply by the maximum bs set. Then
834 divide that number by the huge page size. You can see the
835 size of the huge pages in /proc/meminfo. If no huge pages
836 are allocated by having a non-zero number in nr_hugepages,
837 using mmaphuge or shmhuge will fail. Also see hugepage-size.
839 mmaphuge also needs to have hugetlbfs mounted and the file
840 location should point there. So if it's mounted in /huge,
841 you would use mem=mmaphuge:/huge/somefile.
843 iomem_align=int This indiciates the memory alignment of the IO memory buffers.
844 Note that the given alignment is applied to the first IO unit
845 buffer, if using iodepth the alignment of the following buffers
846 are given by the bs used. In other words, if using a bs that is
847 a multiple of the page sized in the system, all buffers will
848 be aligned to this value. If using a bs that is not page
849 aligned, the alignment of subsequent IO memory buffers is the
850 sum of the iomem_align and bs used.
853 Defines the size of a huge page. Must at least be equal
854 to the system setting, see /proc/meminfo. Defaults to 4MB.
855 Should probably always be a multiple of megabytes, so using
856 hugepage-size=Xm is the preferred way to set this to avoid
857 setting a non-pow-2 bad value.
859 exitall When one job finishes, terminate the rest. The default is
860 to wait for each job to finish, sometimes that is not the
863 bwavgtime=int Average the calculated bandwidth over the given time. Value
864 is specified in milliseconds.
866 iopsavgtime=int Average the calculated IOPS over the given time. Value
867 is specified in milliseconds.
869 create_serialize=bool If true, serialize the file creating for the jobs.
870 This may be handy to avoid interleaving of data
871 files, which may greatly depend on the filesystem
872 used and even the number of processors in the system.
874 create_fsync=bool fsync the data file after creation. This is the
877 create_on_open=bool Don't pre-setup the files for IO, just create open()
878 when it's time to do IO to that file.
880 pre_read=bool If this is given, files will be pre-read into memory before
881 starting the given IO operation. This will also clear
882 the 'invalidate' flag, since it is pointless to pre-read
883 and then drop the cache. This will only work for IO engines
884 that are seekable, since they allow you to read the same data
885 multiple times. Thus it will not work on eg network or splice
888 unlink=bool Unlink the job files when done. Not the default, as repeated
889 runs of that job would then waste time recreating the file
892 loops=int Run the specified number of iterations of this job. Used
893 to repeat the same workload a given number of times. Defaults
896 do_verify=bool Run the verify phase after a write phase. Only makes sense if
897 verify is set. Defaults to 1.
899 verify=str If writing to a file, fio can verify the file contents
900 after each iteration of the job. The allowed values are:
902 md5 Use an md5 sum of the data area and store
903 it in the header of each block.
905 crc64 Use an experimental crc64 sum of the data
906 area and store it in the header of each
909 crc32c Use a crc32c sum of the data area and store
910 it in the header of each block.
912 crc32c-intel Use hardware assisted crc32c calcuation
913 provided on SSE4.2 enabled processors. Falls
914 back to regular software crc32c, if not
915 supported by the system.
917 crc32 Use a crc32 sum of the data area and store
918 it in the header of each block.
920 crc16 Use a crc16 sum of the data area and store
921 it in the header of each block.
923 crc7 Use a crc7 sum of the data area and store
924 it in the header of each block.
926 sha512 Use sha512 as the checksum function.
928 sha256 Use sha256 as the checksum function.
930 sha1 Use optimized sha1 as the checksum function.
932 meta Write extra information about each io
933 (timestamp, block number etc.). The block
934 number is verified. See also verify_pattern.
936 null Only pretend to verify. Useful for testing
937 internals with ioengine=null, not for much
940 This option can be used for repeated burn-in tests of a
941 system to make sure that the written data is also
942 correctly read back. If the data direction given is
943 a read or random read, fio will assume that it should
944 verify a previously written file. If the data direction
945 includes any form of write, the verify will be of the
948 verifysort=bool If set, fio will sort written verify blocks when it deems
949 it faster to read them back in a sorted manner. This is
950 often the case when overwriting an existing file, since
951 the blocks are already laid out in the file system. You
952 can ignore this option unless doing huge amounts of really
953 fast IO where the red-black tree sorting CPU time becomes
956 verify_offset=int Swap the verification header with data somewhere else
957 in the block before writing. Its swapped back before
960 verify_interval=int Write the verification header at a finer granularity
961 than the blocksize. It will be written for chunks the
962 size of header_interval. blocksize should divide this
965 verify_pattern=str If set, fio will fill the io buffers with this
966 pattern. Fio defaults to filling with totally random
967 bytes, but sometimes it's interesting to fill with a known
968 pattern for io verification purposes. Depending on the
969 width of the pattern, fio will fill 1/2/3/4 bytes of the
970 buffer at the time(it can be either a decimal or a hex number).
971 The verify_pattern if larger than a 32-bit quantity has to
972 be a hex number that starts with either "0x" or "0X". Use
975 verify_fatal=bool Normally fio will keep checking the entire contents
976 before quitting on a block verification failure. If this
977 option is set, fio will exit the job on the first observed
980 verify_dump=bool If set, dump the contents of both the original data
981 block and the data block we read off disk to files. This
982 allows later analysis to inspect just what kind of data
983 corruption occurred. Off by default.
985 verify_async=int Fio will normally verify IO inline from the submitting
986 thread. This option takes an integer describing how many
987 async offload threads to create for IO verification instead,
988 causing fio to offload the duty of verifying IO contents
989 to one or more separate threads. If using this offload
990 option, even sync IO engines can benefit from using an
991 iodepth setting higher than 1, as it allows them to have
992 IO in flight while verifies are running.
994 verify_async_cpus=str Tell fio to set the given CPU affinity on the
995 async IO verification threads. See cpus_allowed for the
998 verify_backlog=int Fio will normally verify the written contents of a
999 job that utilizes verify once that job has completed. In
1000 other words, everything is written then everything is read
1001 back and verified. You may want to verify continually
1002 instead for a variety of reasons. Fio stores the meta data
1003 associated with an IO block in memory, so for large
1004 verify workloads, quite a bit of memory would be used up
1005 holding this meta data. If this option is enabled, fio
1006 will write only N blocks before verifying these blocks.
1008 will verify the previously written blocks before continuing
1011 verify_backlog_batch=int Control how many blocks fio will verify
1012 if verify_backlog is set. If not set, will default to
1013 the value of verify_backlog (meaning the entire queue
1014 is read back and verified). If verify_backlog_batch is
1015 less than verify_backlog then not all blocks will be verified,
1016 if verify_backlog_batch is larger than verify_backlog, some
1017 blocks will be verified more than once.
1020 wait_for_previous Wait for preceeding jobs in the job file to exit, before
1021 starting this one. Can be used to insert serialization
1022 points in the job file. A stone wall also implies starting
1023 a new reporting group.
1025 new_group Start a new reporting group. If this option isn't given,
1026 jobs in a file will be part of the same reporting group
1027 unless separated by a stone wall (or if it's a group
1028 by itself, with the numjobs option).
1030 numjobs=int Create the specified number of clones of this job. May be
1031 used to setup a larger number of threads/processes doing
1032 the same thing. We regard that grouping of jobs as a
1035 group_reporting If 'numjobs' is set, it may be interesting to display
1036 statistics for the group as a whole instead of for each
1037 individual job. This is especially true of 'numjobs' is
1038 large, looking at individual thread/process output quickly
1039 becomes unwieldy. If 'group_reporting' is specified, fio
1040 will show the final report per-group instead of per-job.
1042 thread fio defaults to forking jobs, however if this option is
1043 given, fio will use pthread_create(3) to create threads
1046 zonesize=int Divide a file into zones of the specified size. See zoneskip.
1048 zoneskip=int Skip the specified number of bytes when zonesize data has
1049 been read. The two zone options can be used to only do
1050 io on zones of a file.
1052 write_iolog=str Write the issued io patterns to the specified file. See
1053 read_iolog. Specify a separate file for each job, otherwise
1054 the iologs will be interspersed and the file may be corrupt.
1056 read_iolog=str Open an iolog with the specified file name and replay the
1057 io patterns it contains. This can be used to store a
1058 workload and replay it sometime later. The iolog given
1059 may also be a blktrace binary file, which allows fio
1060 to replay a workload captured by blktrace. See blktrace
1061 for how to capture such logging data. For blktrace replay,
1062 the file needs to be turned into a blkparse binary data
1063 file first (blkparse <device> -o /dev/null -d file_for_fio.bin).
1065 replay_no_stall=int When replaying I/O with read_iolog the default behavior
1066 is to attempt to respect the time stamps within the log and
1067 replay them with the appropriate delay between IOPS. By
1068 setting this variable fio will not respect the timestamps and
1069 attempt to replay them as fast as possible while still
1070 respecting ordering. The result is the same I/O pattern to a
1071 given device, but different timings.
1073 replay_redirect=str While replaying I/O patterns using read_iolog the
1074 default behavior is to replay the IOPS onto the major/minor
1075 device that each IOP was recorded from. This is sometimes
1076 undesireable because on a different machine those major/minor
1077 numbers can map to a different device. Changing hardware on
1078 the same system can also result in a different major/minor
1079 mapping. Replay_redirect causes all IOPS to be replayed onto
1080 the single specified device regardless of the device it was
1081 recorded from. i.e. replay_redirect=/dev/sdc would cause all
1082 IO in the blktrace to be replayed onto /dev/sdc. This means
1083 multiple devices will be replayed onto a single, if the trace
1084 contains multiple devices. If you want multiple devices to be
1085 replayed concurrently to multiple redirected devices you must
1086 blkparse your trace into separate traces and replay them with
1087 independent fio invocations. Unfortuantely this also breaks
1088 the strict time ordering between multiple device accesses.
1090 write_bw_log=str If given, write a bandwidth log of the jobs in this job
1091 file. Can be used to store data of the bandwidth of the
1092 jobs in their lifetime. The included fio_generate_plots
1093 script uses gnuplot to turn these text files into nice
1094 graphs. See write_log_log for behaviour of given
1095 filename. For this option, the postfix is _bw.log.
1097 write_lat_log=str Same as write_bw_log, except that this option stores io
1098 submission, completion, and total latencies instead. If no
1099 filename is given with this option, the default filename of
1100 "jobname_type.log" is used. Even if the filename is given,
1101 fio will still append the type of log. So if one specifies
1105 The actual log names will be foo_slat.log, foo_slat.log,
1106 and foo_lat.log. This helps fio_generate_plot fine the logs
1109 write_bw_log=str If given, write an IOPS log of the jobs in this job
1110 file. See write_bw_log.
1112 write_iops_log=str Same as write_bw_log, but writes IOPS. If no filename is
1113 given with this option, the default filename of
1114 "jobname_type.log" is used. Even if the filename is given,
1115 fio will still append the type of log.
1117 log_avg_msec=int By default, fio will log an entry in the iops, latency,
1118 or bw log for every IO that completes. When writing to the
1119 disk log, that can quickly grow to a very large size. Setting
1120 this option makes fio average the each log entry over the
1121 specified period of time, reducing the resolution of the log.
1124 lockmem=int Pin down the specified amount of memory with mlock(2). Can
1125 potentially be used instead of removing memory or booting
1126 with less memory to simulate a smaller amount of memory.
1128 exec_prerun=str Before running this job, issue the command specified
1131 exec_postrun=str After the job completes, issue the command specified
1134 ioscheduler=str Attempt to switch the device hosting the file to the specified
1135 io scheduler before running.
1137 cpuload=int If the job is a CPU cycle eater, attempt to use the specified
1138 percentage of CPU cycles.
1140 cpuchunks=int If the job is a CPU cycle eater, split the load into
1141 cycles of the given time. In microseconds.
1143 disk_util=bool Generate disk utilization statistics, if the platform
1144 supports it. Defaults to on.
1146 disable_lat=bool Disable measurements of total latency numbers. Useful
1147 only for cutting back the number of calls to gettimeofday,
1148 as that does impact performance at really high IOPS rates.
1149 Note that to really get rid of a large amount of these
1150 calls, this option must be used with disable_slat and
1153 disable_clat=bool Disable measurements of completion latency numbers. See
1156 disable_slat=bool Disable measurements of submission latency numbers. See
1159 disable_bw=bool Disable measurements of throughput/bandwidth numbers. See
1162 clat_percentiles=bool Enable the reporting of percentiles of
1163 completion latencies.
1165 percentile_list=float_list Overwrite the default list of percentiles
1166 for completion latencies. Each number is a floating
1167 number in the range (0,100], and the maximum length of
1168 the list is 20. Use ':' to separate the numbers, and
1169 list the numbers in ascending order. For example,
1170 --percentile_list=99.5:99.9 will cause fio to report
1171 the values of completion latency below which 99.5% and
1172 99.9% of the observed latencies fell, respectively.
1174 gtod_reduce=bool Enable all of the gettimeofday() reducing options
1175 (disable_clat, disable_slat, disable_bw) plus reduce
1176 precision of the timeout somewhat to really shrink
1177 the gettimeofday() call count. With this option enabled,
1178 we only do about 0.4% of the gtod() calls we would have
1179 done if all time keeping was enabled.
1181 gtod_cpu=int Sometimes it's cheaper to dedicate a single thread of
1182 execution to just getting the current time. Fio (and
1183 databases, for instance) are very intensive on gettimeofday()
1184 calls. With this option, you can set one CPU aside for
1185 doing nothing but logging current time to a shared memory
1186 location. Then the other threads/processes that run IO
1187 workloads need only copy that segment, instead of entering
1188 the kernel with a gettimeofday() call. The CPU set aside
1189 for doing these time calls will be excluded from other
1190 uses. Fio will manually clear it from the CPU mask of other
1193 continue_on_error=str Normally fio will exit the job on the first observed
1194 failure. If this option is set, fio will continue the job when
1195 there is a 'non-fatal error' (EIO or EILSEQ) until the runtime
1196 is exceeded or the I/O size specified is completed. If this
1197 option is used, there are two more stats that are appended,
1198 the total error count and the first error. The error field
1199 given in the stats is the first error that was hit during the
1202 The allowed values are:
1204 none Exit on any IO or verify errors.
1206 read Continue on read errors, exit on all others.
1208 write Continue on write errors, exit on all others.
1210 io Continue on any IO error, exit on all others.
1212 verify Continue on verify errors, exit on all others.
1214 all Continue on all errors.
1216 0 Backward-compatible alias for 'none'.
1218 1 Backward-compatible alias for 'all'.
1220 cgroup=str Add job to this control group. If it doesn't exist, it will
1221 be created. The system must have a mounted cgroup blkio
1222 mount point for this to work. If your system doesn't have it
1223 mounted, you can do so with:
1225 # mount -t cgroup -o blkio none /cgroup
1227 cgroup_weight=int Set the weight of the cgroup to this value. See
1228 the documentation that comes with the kernel, allowed values
1229 are in the range of 100..1000.
1231 cgroup_nodelete=bool Normally fio will delete the cgroups it has created after
1232 the job completion. To override this behavior and to leave
1233 cgroups around after the job completion, set cgroup_nodelete=1.
1234 This can be useful if one wants to inspect various cgroup
1235 files after job completion. Default: false
1237 uid=int Instead of running as the invoking user, set the user ID to
1238 this value before the thread/process does any work.
1240 gid=int Set group ID, see uid.
1242 flow_id=int The ID of the flow. If not specified, it defaults to being a
1243 global flow. See flow.
1245 flow=int Weight in token-based flow control. If this value is used, then
1246 there is a 'flow counter' which is used to regulate the
1247 proportion of activity between two or more jobs. fio attempts
1248 to keep this flow counter near zero. The 'flow' parameter
1249 stands for how much should be added or subtracted to the flow
1250 counter on each iteration of the main I/O loop. That is, if
1251 one job has flow=8 and another job has flow=-1, then there
1252 will be a roughly 1:8 ratio in how much one runs vs the other.
1254 flow_watermark=int The maximum value that the absolute value of the flow
1255 counter is allowed to reach before the job must wait for a
1256 lower value of the counter.
1258 flow_sleep=int The period of time, in microseconds, to wait after the flow
1259 watermark has been exceeded before retrying operations
1261 In addition, there are some parameters which are only valid when a specific
1262 ioengine is in use. These are used identically to normal parameters, with the
1263 caveat that when used on the command line, they must come after the ioengine
1264 that defines them is selected.
1266 [libaio] userspace_reap Normally, with the libaio engine in use, fio will use
1267 the io_getevents system call to reap newly returned events.
1268 With this flag turned on, the AIO ring will be read directly
1269 from user-space to reap events. The reaping mode is only
1270 enabled when polling for a minimum of 0 events (eg when
1271 iodepth_batch_complete=0).
1273 [netsplice] hostname=str
1274 [net] hostname=str The host name or IP address to use for TCP or UDP based IO.
1275 If the job is a TCP listener or UDP reader, the hostname is not
1276 used and must be omitted.
1278 [netsplice] port=int
1279 [net] port=int The TCP or UDP port to bind to or connect to.
1281 [netsplice] protocol=str
1282 [netsplice] proto=str
1284 [net] proto=str The network protocol to use. Accepted values are:
1286 tcp Transmission control protocol
1287 udp Unreliable datagram protocol
1288 unix UNIX domain socket
1290 When the protocol is TCP or UDP, the port must also be given,
1291 as well as the hostname if the job is a TCP listener or UDP
1292 reader. For unix sockets, the normal filename option should be
1293 used and the port is invalid.
1295 [net] listen For TCP network connections, tell fio to listen for incoming
1296 connections rather than initiating an outgoing connection. The
1297 hostname must be omitted if this option is used.
1300 6.0 Interpreting the output
1301 ---------------------------
1303 fio spits out a lot of output. While running, fio will display the
1304 status of the jobs created. An example of that would be:
1306 Threads: 1: [_r] [24.8% done] [ 13509/ 8334 kb/s] [eta 00h:01m:31s]
1308 The characters inside the square brackets denote the current status of
1309 each thread. The possible values (in typical life cycle order) are:
1313 P Thread setup, but not started.
1315 I Thread initialized, waiting.
1316 p Thread running pre-reading file(s).
1317 R Running, doing sequential reads.
1318 r Running, doing random reads.
1319 W Running, doing sequential writes.
1320 w Running, doing random writes.
1321 M Running, doing mixed sequential reads/writes.
1322 m Running, doing mixed random reads/writes.
1323 F Running, currently waiting for fsync()
1324 V Running, doing verification of written data.
1325 E Thread exited, not reaped by main thread yet.
1328 The other values are fairly self explanatory - number of threads
1329 currently running and doing io, rate of io since last check (read speed
1330 listed first, then write speed), and the estimated completion percentage
1331 and time for the running group. It's impossible to estimate runtime of
1332 the following groups (if any).
1334 When fio is done (or interrupted by ctrl-c), it will show the data for
1335 each thread, group of threads, and disks in that order. For each data
1336 direction, the output looks like:
1338 Client1 (g=0): err= 0:
1339 write: io= 32MB, bw= 666KB/s, iops=89 , runt= 50320msec
1340 slat (msec): min= 0, max= 136, avg= 0.03, stdev= 1.92
1341 clat (msec): min= 0, max= 631, avg=48.50, stdev=86.82
1342 bw (KB/s) : min= 0, max= 1196, per=51.00%, avg=664.02, stdev=681.68
1343 cpu : usr=1.49%, sys=0.25%, ctx=7969, majf=0, minf=17
1344 IO depths : 1=0.1%, 2=0.3%, 4=0.5%, 8=99.0%, 16=0.0%, 32=0.0%, >32=0.0%
1345 submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
1346 complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
1347 issued r/w: total=0/32768, short=0/0
1348 lat (msec): 2=1.6%, 4=0.0%, 10=3.2%, 20=12.8%, 50=38.4%, 100=24.8%,
1349 lat (msec): 250=15.2%, 500=0.0%, 750=0.0%, 1000=0.0%, >=2048=0.0%
1351 The client number is printed, along with the group id and error of that
1352 thread. Below is the io statistics, here for writes. In the order listed,
1355 io= Number of megabytes io performed
1356 bw= Average bandwidth rate
1357 iops= Average IOs performed per second
1358 runt= The runtime of that thread
1359 slat= Submission latency (avg being the average, stdev being the
1360 standard deviation). This is the time it took to submit
1361 the io. For sync io, the slat is really the completion
1362 latency, since queue/complete is one operation there. This
1363 value can be in milliseconds or microseconds, fio will choose
1364 the most appropriate base and print that. In the example
1365 above, milliseconds is the best scale.
1366 clat= Completion latency. Same names as slat, this denotes the
1367 time from submission to completion of the io pieces. For
1368 sync io, clat will usually be equal (or very close) to 0,
1369 as the time from submit to complete is basically just
1370 CPU time (io has already been done, see slat explanation).
1371 bw= Bandwidth. Same names as the xlat stats, but also includes
1372 an approximate percentage of total aggregate bandwidth
1373 this thread received in this group. This last value is
1374 only really useful if the threads in this group are on the
1375 same disk, since they are then competing for disk access.
1376 cpu= CPU usage. User and system time, along with the number
1377 of context switches this thread went through, usage of
1378 system and user time, and finally the number of major
1379 and minor page faults.
1380 IO depths= The distribution of io depths over the job life time. The
1381 numbers are divided into powers of 2, so for example the
1382 16= entries includes depths up to that value but higher
1383 than the previous entry. In other words, it covers the
1384 range from 16 to 31.
1385 IO submit= How many pieces of IO were submitting in a single submit
1386 call. Each entry denotes that amount and below, until
1387 the previous entry - eg, 8=100% mean that we submitted
1388 anywhere in between 5-8 ios per submit call.
1389 IO complete= Like the above submit number, but for completions instead.
1390 IO issued= The number of read/write requests issued, and how many
1392 IO latencies= The distribution of IO completion latencies. This is the
1393 time from when IO leaves fio and when it gets completed.
1394 The numbers follow the same pattern as the IO depths,
1395 meaning that 2=1.6% means that 1.6% of the IO completed
1396 within 2 msecs, 20=12.8% means that 12.8% of the IO
1397 took more than 10 msecs, but less than (or equal to) 20 msecs.
1399 After each client has been listed, the group statistics are printed. They
1400 will look like this:
1402 Run status group 0 (all jobs):
1403 READ: io=64MB, aggrb=22178, minb=11355, maxb=11814, mint=2840msec, maxt=2955msec
1404 WRITE: io=64MB, aggrb=1302, minb=666, maxb=669, mint=50093msec, maxt=50320msec
1406 For each data direction, it prints:
1408 io= Number of megabytes io performed.
1409 aggrb= Aggregate bandwidth of threads in this group.
1410 minb= The minimum average bandwidth a thread saw.
1411 maxb= The maximum average bandwidth a thread saw.
1412 mint= The smallest runtime of the threads in that group.
1413 maxt= The longest runtime of the threads in that group.
1415 And finally, the disk statistics are printed. They will look like this:
1417 Disk stats (read/write):
1418 sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00%
1420 Each value is printed for both reads and writes, with reads first. The
1423 ios= Number of ios performed by all groups.
1424 merge= Number of merges io the io scheduler.
1425 ticks= Number of ticks we kept the disk busy.
1426 io_queue= Total time spent in the disk queue.
1427 util= The disk utilization. A value of 100% means we kept the disk
1428 busy constantly, 50% would be a disk idling half of the time.
1434 For scripted usage where you typically want to generate tables or graphs
1435 of the results, fio can output the results in a semicolon separated format.
1436 The format is one long line of values, such as:
1438 2;card0;0;0;7139336;121836;60004;1;10109;27.932460;116.933948;220;126861;3495.446807;1085.368601;226;126864;3523.635629;1089.012448;24063;99944;50.275485%;59818.274627;5540.657370;7155060;122104;60004;1;8338;29.086342;117.839068;388;128077;5032.488518;1234.785715;391;128085;5061.839412;1236.909129;23436;100928;50.287926%;59964.832030;5644.844189;14.595833%;19.394167%;123706;0;7313;0.1%;0.1%;0.1%;0.1%;0.1%;0.1%;100.0%;0.00%;0.00%;0.00%;0.00%;0.00%;0.00%;0.01%;0.02%;0.05%;0.16%;6.04%;40.40%;52.68%;0.64%;0.01%;0.00%;0.01%;0.00%;0.00%;0.00%;0.00%;0.00%
1439 A description of this job goes here.
1441 The job description (if provided) follows on a second line.
1443 To enable terse output, use the --minimal command line option. The first
1444 value is the version of the terse output format. If the output has to
1445 be changed for some reason, this number will be incremented by 1 to
1446 signify that change.
1448 Split up, the format is as follows:
1450 terse version, fio version, jobname, groupid, error
1452 Total IO (KB), bandwidth (KB/sec), IOPS, runtime (msec)
1453 Submission latency: min, max, mean, deviation
1454 Completion latency: min, max, mean, deviation
1455 Completion latency percentiles: 20 fields (see below)
1456 Total latency: min, max, mean, deviation
1457 Bw: min, max, aggregate percentage of total, mean, deviation
1459 Total IO (KB), bandwidth (KB/sec), IOPS, runtime (msec)
1460 Submission latency: min, max, mean, deviation
1461 Completion latency: min, max, mean, deviation
1462 Completion latency percentiles: 20 fields (see below)
1463 Total latency: min, max, mean, deviation
1464 Bw: min, max, aggregate percentage of total, mean, deviation
1465 CPU usage: user, system, context switches, major faults, minor faults
1466 IO depths: <=1, 2, 4, 8, 16, 32, >=64
1467 IO latencies microseconds: <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000
1468 IO latencies milliseconds: <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, 2000, >=2000
1469 Disk utilization: Disk name, Read ios, write ios,
1470 Read merges, write merges,
1471 Read ticks, write ticks,
1472 Time spent in queue, disk utilization percentage
1473 Additional Info (dependant on continue_on_error, default off): total # errors, first error code
1475 Additional Info (dependant on description being set): Text description
1477 Completion latency percentiles can be a grouping of up to 20 sets, so
1478 for the terse output fio writes all of them. Each field will look like this:
1482 which is the Xth percentile, and the usec latency associated with it.
1484 For disk utilization, all disks used by fio are shown. So for each disk
1485 there will be a disk utilization section.
1488 8.0 Trace file format
1489 ---------------------
1490 There are two trace file format that you can encounter. The older (v1) format
1491 is unsupported since version 1.20-rc3 (March 2008). It will still be described
1492 below in case that you get an old trace and want to understand it.
1494 In any case the trace is a simple text file with a single action per line.
1497 8.1 Trace file format v1
1498 ------------------------
1499 Each line represents a single io action in the following format:
1503 where rw=0/1 for read/write, and the offset and length entries being in bytes.
1505 This format is not supported in Fio versions => 1.20-rc3.
1508 8.2 Trace file format v2
1509 ------------------------
1510 The second version of the trace file format was added in Fio version 1.17.
1511 It allows to access more then one file per trace and has a bigger set of
1512 possible file actions.
1514 The first line of the trace file has to be:
1518 Following this can be lines in two different formats, which are described below.
1520 The file management format:
1524 The filename is given as an absolute path. The action can be one of these:
1526 add Add the given filename to the trace
1527 open Open the file with the given filename. The filename has to have
1528 been added with the add action before.
1529 close Close the file with the given filename. The file has to have been
1533 The file io action format:
1535 filename action offset length
1537 The filename is given as an absolute path, and has to have been added and opened
1538 before it can be used with this format. The offset and length are given in
1539 bytes. The action can be one of these:
1541 wait Wait for 'offset' microseconds. Everything below 100 is discarded.
1542 read Read 'length' bytes beginning from 'offset'
1543 write Write 'length' bytes beginning from 'offset'
1544 sync fsync() the file
1545 datasync fdatasync() the file
1546 trim trim the given file from the given 'offset' for 'length' bytes
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