1 Table of contents 2 ----------------- 3 4 1. Overview 5 2. How fio works 6 3. Running fio 7 4. Job file format 8 5. Detailed list of parameters 9 6. Normal output 10 7. Terse output 11 8. Trace file format 12 9. CPU idleness profiling 13 14 1.0 Overview and history 15 ------------------------ 16 fio was originally written to save me the hassle of writing special test 17 case programs when I wanted to test a specific workload, either for 18 performance reasons or to find/reproduce a bug. The process of writing 19 such a test app can be tiresome, especially if you have to do it often. 20 Hence I needed a tool that would be able to simulate a given io workload 21 without resorting to writing a tailored test case again and again. 22 23 A test work load is difficult to define, though. There can be any number 24 of processes or threads involved, and they can each be using their own 25 way of generating io. You could have someone dirtying large amounts of 26 memory in an memory mapped file, or maybe several threads issuing 27 reads using asynchronous io. fio needed to be flexible enough to 28 simulate both of these cases, and many more. 29 30 2.0 How fio works 31 ----------------- 32 The first step in getting fio to simulate a desired io workload, is 33 writing a job file describing that specific setup. A job file may contain 34 any number of threads and/or files - the typical contents of the job file 35 is a global section defining shared parameters, and one or more job 36 sections describing the jobs involved. When run, fio parses this file 37 and sets everything up as described. If we break down a job from top to 38 bottom, it contains the following basic parameters: 39 40 IO type Defines the io pattern issued to the file(s). 41 We may only be reading sequentially from this 42 file(s), or we may be writing randomly. Or even 43 mixing reads and writes, sequentially or randomly. 44 45 Block size In how large chunks are we issuing io? This may be 46 a single value, or it may describe a range of 47 block sizes. 48 49 IO size How much data are we going to be reading/writing. 50 51 IO engine How do we issue io? We could be memory mapping the 52 file, we could be using regular read/write, we 53 could be using splice, async io, syslet, or even 54 SG (SCSI generic sg). 55 56 IO depth If the io engine is async, how large a queuing 57 depth do we want to maintain? 58 59 IO type Should we be doing buffered io, or direct/raw io? 60 61 Num files How many files are we spreading the workload over. 62 63 Num threads How many threads or processes should we spread 64 this workload over. 65 66 The above are the basic parameters defined for a workload, in addition 67 there's a multitude of parameters that modify other aspects of how this 68 job behaves. 69 70 71 3.0 Running fio 72 --------------- 73 See the README file for command line parameters, there are only a few 74 of them. 75 76 Running fio is normally the easiest part - you just give it the job file 77 (or job files) as parameters: 78 79 $ fio job_file 80 81 and it will start doing what the job_file tells it to do. You can give 82 more than one job file on the command line, fio will serialize the running 83 of those files. Internally that is the same as using the 'stonewall' 84 parameter described in the parameter section. 85 86 If the job file contains only one job, you may as well just give the 87 parameters on the command line. The command line parameters are identical 88 to the job parameters, with a few extra that control global parameters 89 (see README). For example, for the job file parameter iodepth=2, the 90 mirror command line option would be --iodepth 2 or --iodepth=2. You can 91 also use the command line for giving more than one job entry. For each 92 --name option that fio sees, it will start a new job with that name. 93 Command line entries following a --name entry will apply to that job, 94 until there are no more entries or a new --name entry is seen. This is 95 similar to the job file options, where each option applies to the current 96 job until a new [] job entry is seen. 97 98 fio does not need to run as root, except if the files or devices specified 99 in the job section requires that. Some other options may also be restricted, 100 such as memory locking, io scheduler switching, and decreasing the nice value. 101 102 103 4.0 Job file format 104 ------------------- 105 As previously described, fio accepts one or more job files describing 106 what it is supposed to do. The job file format is the classic ini file, 107 where the names enclosed in [] brackets define the job name. You are free 108 to use any ascii name you want, except 'global' which has special meaning. 109 A global section sets defaults for the jobs described in that file. A job 110 may override a global section parameter, and a job file may even have 111 several global sections if so desired. A job is only affected by a global 112 section residing above it. If the first character in a line is a ';' or a 113 '#', the entire line is discarded as a comment. 114 115 So let's look at a really simple job file that defines two processes, each 116 randomly reading from a 128MB file. 117 118 ; -- start job file -- 119 [global] 120 rw=randread 121 size=128m 122 123 [job1] 124 125 [job2] 126 127 ; -- end job file -- 128 129 As you can see, the job file sections themselves are empty as all the 130 described parameters are shared. As no filename= option is given, fio 131 makes up a filename for each of the jobs as it sees fit. On the command 132 line, this job would look as follows: 133 134 $ fio --name=global --rw=randread --size=128m --name=job1 --name=job2 135 136 137 Let's look at an example that has a number of processes writing randomly 138 to files. 139 140 ; -- start job file -- 141 [random-writers] 142 ioengine=libaio 143 iodepth=4 144 rw=randwrite 145 bs=32k 146 direct=0 147 size=64m 148 numjobs=4 149 150 ; -- end job file -- 151 152 Here we have no global section, as we only have one job defined anyway. 153 We want to use async io here, with a depth of 4 for each file. We also 154 increased the buffer size used to 32KB and define numjobs to 4 to 155 fork 4 identical jobs. The result is 4 processes each randomly writing 156 to their own 64MB file. Instead of using the above job file, you could 157 have given the parameters on the command line. For this case, you would 158 specify: 159 160 $ fio --name=random-writers --ioengine=libaio --iodepth=4 --rw=randwrite --bs=32k --direct=0 --size=64m --numjobs=4 161 162 When fio is utilized as a basis of any reasonably large test suite, it might be 163 desirable to share a set of standardized settings across multiple job files. 164 Instead of copy/pasting such settings, any section may pull in an external 165 .fio file with 'include filename' directive, as in the following example: 166 167 ; -- start job file including.fio -- 168 [global] 169 filename=/tmp/test 170 filesize=1m 171 include glob-include.fio 172 173 [test] 174 rw=randread 175 bs=4k 176 time_based=1 177 runtime=10 178 include test-include.fio 179 ; -- end job file including.fio -- 180 181 ; -- start job file glob-include.fio -- 182 thread=1 183 group_reporting=1 184 ; -- end job file glob-include.fio -- 185 186 ; -- start job file test-include.fio -- 187 ioengine=libaio 188 iodepth=4 189 ; -- end job file test-include.fio -- 190 191 Settings pulled into a section apply to that section only (except global 192 section). Include directives may be nested in that any included file may 193 contain further include directive(s). Include files may not contain [] 194 sections. 195 196 197 4.1 Environment variables 198 ------------------------- 199 200 fio also supports environment variable expansion in job files. Any 201 substring of the form "${VARNAME}" as part of an option value (in other 202 words, on the right of the `='), will be expanded to the value of the 203 environment variable called VARNAME. If no such environment variable 204 is defined, or VARNAME is the empty string, the empty string will be 205 substituted. 206 207 As an example, let's look at a sample fio invocation and job file: 208 209 $ SIZE=64m NUMJOBS=4 fio jobfile.fio 210 211 ; -- start job file -- 212 [random-writers] 213 rw=randwrite 214 size=${SIZE} 215 numjobs=${NUMJOBS} 216 ; -- end job file -- 217 218 This will expand to the following equivalent job file at runtime: 219 220 ; -- start job file -- 221 [random-writers] 222 rw=randwrite 223 size=64m 224 numjobs=4 225 ; -- end job file -- 226 227 fio ships with a few example job files, you can also look there for 228 inspiration. 229 230 4.2 Reserved keywords 231 --------------------- 232 233 Additionally, fio has a set of reserved keywords that will be replaced 234 internally with the appropriate value. Those keywords are: 235 236 $pagesize The architecture page size of the running system 237 $mb_memory Megabytes of total memory in the system 238 $ncpus Number of online available CPUs 239 240 These can be used on the command line or in the job file, and will be 241 automatically substituted with the current system values when the job 242 is run. Simple math is also supported on these keywords, so you can 243 perform actions like: 244 245 size=8*$mb_memory 246 247 and get that properly expanded to 8 times the size of memory in the 248 machine. 249 250 251 5.0 Detailed list of parameters 252 ------------------------------- 253 254 This section describes in details each parameter associated with a job. 255 Some parameters take an option of a given type, such as an integer or 256 a string. Anywhere a numeric value is required, an arithmetic expression 257 may be used, provided it is surrounded by parentheses. Supported operators 258 are: 259 260 addition (+) 261 subtraction (-) 262 multiplication (*) 263 division (/) 264 modulus (%) 265 exponentiation (^) 266 267 For time values in expressions, units are microseconds by default. This is 268 different than for time values not in expressions (not enclosed in 269 parentheses). The following types are used: 270 271 str String. This is a sequence of alpha characters. 272 time Integer with possible time suffix. In seconds unless otherwise 273 specified, use eg 10m for 10 minutes. Accepts s/m/h for seconds, 274 minutes, and hours, and accepts 'ms' (or 'msec') for milliseconds, 275 and 'us' (or 'usec') for microseconds. 276 int SI integer. A whole number value, which may contain a suffix 277 describing the base of the number. Accepted suffixes are k/m/g/t/p, 278 meaning kilo, mega, giga, tera, and peta. The suffix is not case 279 sensitive, and you may also include trailing 'b' (eg 'kb' is the same 280 as 'k'). So if you want to specify 4096, you could either write 281 out '4096' or just give 4k. The suffixes signify base 2 values, so 282 1024 is 1k and 1024k is 1m and so on, unless the suffix is explicitly 283 set to a base 10 value using 'kib', 'mib', 'gib', etc. If that is the 284 case, then 1000 is used as the multiplier. This can be handy for 285 disks, since manufacturers generally use base 10 values when listing 286 the capacity of a drive. If the option accepts an upper and lower 287 range, use a colon ':' or minus '-' to separate such values. May also 288 include a prefix to indicate numbers base. If 0x is used, the number 289 is assumed to be hexadecimal. See irange. 290 bool Boolean. Usually parsed as an integer, however only defined for 291 true and false (1 and 0). 292 irange Integer range with suffix. Allows value range to be given, such 293 as 1024-4096. A colon may also be used as the separator, eg 294 1k:4k. If the option allows two sets of ranges, they can be 295 specified with a ',' or '/' delimiter: 1k-4k/8k-32k. Also see 296 int. 297 float_list A list of floating numbers, separated by a ':' character. 298 299 With the above in mind, here follows the complete list of fio job 300 parameters. 301 302 name=str ASCII name of the job. This may be used to override the 303 name printed by fio for this job. Otherwise the job 304 name is used. On the command line this parameter has the 305 special purpose of also signaling the start of a new 306 job. 307 308 description=str Text description of the job. Doesn't do anything except 309 dump this text description when this job is run. It's 310 not parsed. 311 312 directory=str Prefix filenames with this directory. Used to place files 313 in a different location than "./". See the 'filename' option 314 for escaping certain characters. 315 316 filename=str Fio normally makes up a filename based on the job name, 317 thread number, and file number. If you want to share 318 files between threads in a job or several jobs, specify 319 a filename for each of them to override the default. If 320 the ioengine used is 'net', the filename is the host, port, 321 and protocol to use in the format of =host,port,protocol. 322 See ioengine=net for more. If the ioengine is file based, you 323 can specify a number of files by separating the names with a 324 ':' colon. So if you wanted a job to open /dev/sda and /dev/sdb 325 as the two working files, you would use 326 filename=/dev/sda:/dev/sdb. On Windows, disk devices are 327 accessed as \\.\PhysicalDrive0 for the first device, 328 \\.\PhysicalDrive1 for the second etc. Note: Windows and 329 FreeBSD prevent write access to areas of the disk containing 330 in-use data (e.g. filesystems). 331 If the wanted filename does need to include a colon, then 332 escape that with a '\' character. For instance, if the filename 333 is "/dev/dsk/foo@3,0:c", then you would use 334 filename="/dev/dsk/foo@3,0\:c". '-' is a reserved name, meaning 335 stdin or stdout. Which of the two depends on the read/write 336 direction set. 337 338 filename_format=str 339 If sharing multiple files between jobs, it is usually necessary 340 to have fio generate the exact names that you want. By default, 341 fio will name a file based on the default file format 342 specification of jobname.jobnumber.filenumber. With this 343 option, that can be customized. Fio will recognize and replace 344 the following keywords in this string: 345 346 $jobname 347 The name of the worker thread or process. 348 349 $jobnum 350 The incremental number of the worker thread or 351 process. 352 353 $filenum 354 The incremental number of the file for that worker 355 thread or process. 356 357 To have dependent jobs share a set of files, this option can 358 be set to have fio generate filenames that are shared between 359 the two. For instance, if testfiles.$filenum is specified, 360 file number 4 for any job will be named testfiles.4. The 361 default of $jobname.$jobnum.$filenum will be used if 362 no other format specifier is given. 363 364 opendir=str Tell fio to recursively add any file it can find in this 365 directory and down the file system tree. 366 367 lockfile=str Fio defaults to not locking any files before it does 368 IO to them. If a file or file descriptor is shared, fio 369 can serialize IO to that file to make the end result 370 consistent. This is usual for emulating real workloads that 371 share files. The lock modes are: 372 373 none No locking. The default. 374 exclusive Only one thread/process may do IO, 375 excluding all others. 376 readwrite Read-write locking on the file. Many 377 readers may access the file at the 378 same time, but writes get exclusive 379 access. 380 381 readwrite=str 382 rw=str Type of io pattern. Accepted values are: 383 384 read Sequential reads 385 write Sequential writes 386 randwrite Random writes 387 randread Random reads 388 rw,readwrite Sequential mixed reads and writes 389 randrw Random mixed reads and writes 390 391 For the mixed io types, the default is to split them 50/50. 392 For certain types of io the result may still be skewed a bit, 393 since the speed may be different. It is possible to specify 394 a number of IO's to do before getting a new offset, this is 395 done by appending a ':<nr>' to the end of the string given. 396 For a random read, it would look like 'rw=randread:8' for 397 passing in an offset modifier with a value of 8. If the 398 suffix is used with a sequential IO pattern, then the value 399 specified will be added to the generated offset for each IO. 400 For instance, using rw=write:4k will skip 4k for every 401 write. It turns sequential IO into sequential IO with holes. 402 See the 'rw_sequencer' option. 403 404 rw_sequencer=str If an offset modifier is given by appending a number to 405 the rw=<str> line, then this option controls how that 406 number modifies the IO offset being generated. Accepted 407 values are: 408 409 sequential Generate sequential offset 410 identical Generate the same offset 411 412 'sequential' is only useful for random IO, where fio would 413 normally generate a new random offset for every IO. If you 414 append eg 8 to randread, you would get a new random offset for 415 every 8 IO's. The result would be a seek for only every 8 416 IO's, instead of for every IO. Use rw=randread:8 to specify 417 that. As sequential IO is already sequential, setting 418 'sequential' for that would not result in any differences. 419 'identical' behaves in a similar fashion, except it sends 420 the same offset 8 number of times before generating a new 421 offset. 422 423 kb_base=int The base unit for a kilobyte. The defacto base is 2^10, 1024. 424 Storage manufacturers like to use 10^3 or 1000 as a base 425 ten unit instead, for obvious reasons. Allow values are 426 1024 or 1000, with 1024 being the default. 427 428 unified_rw_reporting=bool Fio normally reports statistics on a per 429 data direction basis, meaning that read, write, and trim are 430 accounted and reported separately. If this option is set, 431 the fio will sum the results and report them as "mixed" 432 instead. 433 434 randrepeat=bool For random IO workloads, seed the generator in a predictable 435 way so that results are repeatable across repetitions. 436 437 randseed=int Seed the random number generators based on this seed value, to 438 be able to control what sequence of output is being generated. 439 If not set, the random sequence depends on the randrepeat 440 setting. 441 442 fallocate=str Whether pre-allocation is performed when laying down files. 443 Accepted values are: 444 445 none Do not pre-allocate space 446 posix Pre-allocate via posix_fallocate() 447 keep Pre-allocate via fallocate() with 448 FALLOC_FL_KEEP_SIZE set 449 0 Backward-compatible alias for 'none' 450 1 Backward-compatible alias for 'posix' 451 452 May not be available on all supported platforms. 'keep' is only 453 available on Linux.If using ZFS on Solaris this must be set to 454 'none' because ZFS doesn't support it. Default: 'posix'. 455 456 fadvise_hint=bool By default, fio will use fadvise() to advise the kernel 457 on what IO patterns it is likely to issue. Sometimes you 458 want to test specific IO patterns without telling the 459 kernel about it, in which case you can disable this option. 460 If set, fio will use POSIX_FADV_SEQUENTIAL for sequential 461 IO and POSIX_FADV_RANDOM for random IO. 462 463 size=int The total size of file io for this job. Fio will run until 464 this many bytes has been transferred, unless runtime is 465 limited by other options (such as 'runtime', for instance, 466 or increased/decreased by 'io_size'). Unless specific nrfiles 467 and filesize options are given, fio will divide this size 468 between the available files specified by the job. If not set, 469 fio will use the full size of the given files or devices. 470 If the files do not exist, size must be given. It is also 471 possible to give size as a percentage between 1 and 100. If 472 size=20% is given, fio will use 20% of the full size of the 473 given files or devices. 474 475 io_size=int 476 io_limit=int Normally fio operates within the region set by 'size', which 477 means that the 'size' option sets both the region and size of 478 IO to be performed. Sometimes that is not what you want. With 479 this option, it is possible to define just the amount of IO 480 that fio should do. For instance, if 'size' is set to 20G and 481 'io_size' is set to 5G, fio will perform IO within the first 482 20G but exit when 5G have been done. The opposite is also 483 possible - if 'size' is set to 20G, and 'io_size' is set to 484 40G, then fio will do 40G of IO within the 0..20G region. 485 486 filesize=int Individual file sizes. May be a range, in which case fio 487 will select sizes for files at random within the given range 488 and limited to 'size' in total (if that is given). If not 489 given, each created file is the same size. 490 491 file_append=bool Perform IO after the end of the file. Normally fio will 492 operate within the size of a file. If this option is set, then 493 fio will append to the file instead. This has identical 494 behavior to setting offset to the size of a file. This option 495 is ignored on non-regular files. 496 497 fill_device=bool 498 fill_fs=bool Sets size to something really large and waits for ENOSPC (no 499 space left on device) as the terminating condition. Only makes 500 sense with sequential write. For a read workload, the mount 501 point will be filled first then IO started on the result. This 502 option doesn't make sense if operating on a raw device node, 503 since the size of that is already known by the file system. 504 Additionally, writing beyond end-of-device will not return 505 ENOSPC there. 506 507 blocksize=int 508 bs=int The block size used for the io units. Defaults to 4k. Values 509 can be given for both read and writes. If a single int is 510 given, it will apply to both. If a second int is specified 511 after a comma, it will apply to writes only. In other words, 512 the format is either bs=read_and_write or bs=read,write,trim. 513 bs=4k,8k will thus use 4k blocks for reads, 8k blocks for 514 writes, and 8k for trims. You can terminate the list with 515 a trailing comma. bs=4k,8k, would use the default value for 516 trims.. If you only wish to set the write size, you 517 can do so by passing an empty read size - bs=,8k will set 518 8k for writes and leave the read default value. 519 520 blockalign=int 521 ba=int At what boundary to align random IO offsets. Defaults to 522 the same as 'blocksize' the minimum blocksize given. 523 Minimum alignment is typically 512b for using direct IO, 524 though it usually depends on the hardware block size. This 525 option is mutually exclusive with using a random map for 526 files, so it will turn off that option. 527 528 blocksize_range=irange 529 bsrange=irange Instead of giving a single block size, specify a range 530 and fio will mix the issued io block sizes. The issued 531 io unit will always be a multiple of the minimum value 532 given (also see bs_unaligned). Applies to both reads and 533 writes, however a second range can be given after a comma. 534 See bs=. 535 536 bssplit=str Sometimes you want even finer grained control of the 537 block sizes issued, not just an even split between them. 538 This option allows you to weight various block sizes, 539 so that you are able to define a specific amount of 540 block sizes issued. The format for this option is: 541 542 bssplit=blocksize/percentage:blocksize/percentage 543 544 for as many block sizes as needed. So if you want to define 545 a workload that has 50% 64k blocks, 10% 4k blocks, and 546 40% 32k blocks, you would write: 547 548 bssplit=4k/10:64k/50:32k/40 549 550 Ordering does not matter. If the percentage is left blank, 551 fio will fill in the remaining values evenly. So a bssplit 552 option like this one: 553 554 bssplit=4k/50:1k/:32k/ 555 556 would have 50% 4k ios, and 25% 1k and 32k ios. The percentages 557 always add up to 100, if bssplit is given a range that adds 558 up to more, it will error out. 559 560 bssplit also supports giving separate splits to reads and 561 writes. The format is identical to what bs= accepts. You 562 have to separate the read and write parts with a comma. So 563 if you want a workload that has 50% 2k reads and 50% 4k reads, 564 while having 90% 4k writes and 10% 8k writes, you would 565 specify: 566 567 bssplit=2k/50:4k/50,4k/90:8k/10 568 569 blocksize_unaligned 570 bs_unaligned If this option is given, any byte size value within bsrange 571 may be used as a block range. This typically wont work with 572 direct IO, as that normally requires sector alignment. 573 574 bs_is_seq_rand If this option is set, fio will use the normal read,write 575 blocksize settings as sequential,random instead. Any random 576 read or write will use the WRITE blocksize settings, and any 577 sequential read or write will use the READ blocksize setting. 578 579 zero_buffers If this option is given, fio will init the IO buffers to 580 all zeroes. The default is to fill them with random data. 581 The resulting IO buffers will not be completely zeroed, 582 unless scramble_buffers is also turned off. 583 584 refill_buffers If this option is given, fio will refill the IO buffers 585 on every submit. The default is to only fill it at init 586 time and reuse that data. Only makes sense if zero_buffers 587 isn't specified, naturally. If data verification is enabled, 588 refill_buffers is also automatically enabled. 589 590 scramble_buffers=bool If refill_buffers is too costly and the target is 591 using data deduplication, then setting this option will 592 slightly modify the IO buffer contents to defeat normal 593 de-dupe attempts. This is not enough to defeat more clever 594 block compression attempts, but it will stop naive dedupe of 595 blocks. Default: true. 596 597 buffer_compress_percentage=int If this is set, then fio will attempt to 598 provide IO buffer content (on WRITEs) that compress to 599 the specified level. Fio does this by providing a mix of 600 random data and a fixed pattern. The fixed pattern is either 601 zeroes, or the pattern specified by buffer_pattern. If the 602 pattern option is used, it might skew the compression ratio 603 slightly. Note that this is per block size unit, for file/disk 604 wide compression level that matches this setting, you'll also 605 want to set refill_buffers. 606 607 buffer_compress_chunk=int See buffer_compress_percentage. This 608 setting allows fio to manage how big the ranges of random 609 data and zeroed data is. Without this set, fio will 610 provide buffer_compress_percentage of blocksize random 611 data, followed by the remaining zeroed. With this set 612 to some chunk size smaller than the block size, fio can 613 alternate random and zeroed data throughout the IO 614 buffer. 615 616 buffer_pattern=str If set, fio will fill the io buffers with this 617 pattern. If not set, the contents of io buffers is defined by 618 the other options related to buffer contents. The setting can 619 be any pattern of bytes, and can be prefixed with 0x for hex 620 values. It may also be a string, where the string must then 621 be wrapped with "". 622 623 dedupe_percentage=int If set, fio will generate this percentage of 624 identical buffers when writing. These buffers will be 625 naturally dedupable. The contents of the buffers depend on 626 what other buffer compression settings have been set. It's 627 possible to have the individual buffers either fully 628 compressible, or not at all. This option only controls the 629 distribution of unique buffers. 630 631 nrfiles=int Number of files to use for this job. Defaults to 1. 632 633 openfiles=int Number of files to keep open at the same time. Defaults to 634 the same as nrfiles, can be set smaller to limit the number 635 simultaneous opens. 636 637 file_service_type=str Defines how fio decides which file from a job to 638 service next. The following types are defined: 639 640 random Just choose a file at random. 641 642 roundrobin Round robin over open files. This 643 is the default. 644 645 sequential Finish one file before moving on to 646 the next. Multiple files can still be 647 open depending on 'openfiles'. 648 649 The string can have a number appended, indicating how 650 often to switch to a new file. So if option random:4 is 651 given, fio will switch to a new random file after 4 ios 652 have been issued. 653 654 ioengine=str Defines how the job issues io to the file. The following 655 types are defined: 656 657 sync Basic read(2) or write(2) io. lseek(2) is 658 used to position the io location. 659 660 psync Basic pread(2) or pwrite(2) io. 661 662 vsync Basic readv(2) or writev(2) IO. 663 664 psyncv Basic preadv(2) or pwritev(2) IO. 665 666 libaio Linux native asynchronous io. Note that Linux 667 may only support queued behaviour with 668 non-buffered IO (set direct=1 or buffered=0). 669 This engine defines engine specific options. 670 671 posixaio glibc posix asynchronous io. 672 673 solarisaio Solaris native asynchronous io. 674 675 windowsaio Windows native asynchronous io. 676 677 mmap File is memory mapped and data copied 678 to/from using memcpy(3). 679 680 splice splice(2) is used to transfer the data and 681 vmsplice(2) to transfer data from user 682 space to the kernel. 683 684 syslet-rw Use the syslet system calls to make 685 regular read/write async. 686 687 sg SCSI generic sg v3 io. May either be 688 synchronous using the SG_IO ioctl, or if 689 the target is an sg character device 690 we use read(2) and write(2) for asynchronous 691 io. 692 693 null Doesn't transfer any data, just pretends 694 to. This is mainly used to exercise fio 695 itself and for debugging/testing purposes. 696 697 net Transfer over the network to given host:port. 698 Depending on the protocol used, the hostname, 699 port, listen and filename options are used to 700 specify what sort of connection to make, while 701 the protocol option determines which protocol 702 will be used. 703 This engine defines engine specific options. 704 705 netsplice Like net, but uses splice/vmsplice to 706 map data and send/receive. 707 This engine defines engine specific options. 708 709 cpuio Doesn't transfer any data, but burns CPU 710 cycles according to the cpuload= and 711 cpucycle= options. Setting cpuload=85 712 will cause that job to do nothing but burn 713 85% of the CPU. In case of SMP machines, 714 use numjobs=<no_of_cpu> to get desired CPU 715 usage, as the cpuload only loads a single 716 CPU at the desired rate. 717 718 guasi The GUASI IO engine is the Generic Userspace 719 Asyncronous Syscall Interface approach 720 to async IO. See 721 722 http://www.xmailserver.org/guasi-lib.html 723 724 for more info on GUASI. 725 726 rdma The RDMA I/O engine supports both RDMA 727 memory semantics (RDMA_WRITE/RDMA_READ) and 728 channel semantics (Send/Recv) for the 729 InfiniBand, RoCE and iWARP protocols. 730 731 falloc IO engine that does regular fallocate to 732 simulate data transfer as fio ioengine. 733 DDIR_READ does fallocate(,mode = keep_size,) 734 DDIR_WRITE does fallocate(,mode = 0) 735 DDIR_TRIM does fallocate(,mode = punch_hole) 736 737 e4defrag IO engine that does regular EXT4_IOC_MOVE_EXT 738 ioctls to simulate defragment activity in 739 request to DDIR_WRITE event 740 741 rbd IO engine supporting direct access to Ceph 742 Rados Block Devices (RBD) via librbd without 743 the need to use the kernel rbd driver. This 744 ioengine defines engine specific options. 745 746 gfapi Using Glusterfs libgfapi sync interface to 747 direct access to Glusterfs volumes without 748 options. 749 750 gfapi_async Using Glusterfs libgfapi async interface 751 to direct access to Glusterfs volumes without 752 having to go through FUSE. This ioengine 753 defines engine specific options. 754 755 libhdfs Read and write through Hadoop (HDFS). 756 The 'filename' option is used to specify host, 757 port of the hdfs name-node to connect. This 758 engine interprets offsets a little 759 differently. In HDFS, files once created 760 cannot be modified. So random writes are not 761 possible. To imitate this, libhdfs engine 762 expects bunch of small files to be created 763 over HDFS, and engine will randomly pick a 764 file out of those files based on the offset 765 generated by fio backend. (see the example 766 job file to create such files, use rw=write 767 option). Please note, you might want to set 768 necessary environment variables to work with 769 hdfs/libhdfs properly. 770 771 external Prefix to specify loading an external 772 IO engine object file. Append the engine 773 filename, eg ioengine=external:/tmp/foo.o 774 to load ioengine foo.o in /tmp. 775 776 iodepth=int This defines how many io units to keep in flight against 777 the file. The default is 1 for each file defined in this 778 job, can be overridden with a larger value for higher 779 concurrency. Note that increasing iodepth beyond 1 will not 780 affect synchronous ioengines (except for small degress when 781 verify_async is in use). Even async engines may impose OS 782 restrictions causing the desired depth not to be achieved. 783 This may happen on Linux when using libaio and not setting 784 direct=1, since buffered IO is not async on that OS. Keep an 785 eye on the IO depth distribution in the fio output to verify 786 that the achieved depth is as expected. Default: 1. 787 788 iodepth_batch_submit=int 789 iodepth_batch=int This defines how many pieces of IO to submit at once. 790 It defaults to 1 which means that we submit each IO 791 as soon as it is available, but can be raised to submit 792 bigger batches of IO at the time. 793 794 iodepth_batch_complete=int This defines how many pieces of IO to retrieve 795 at once. It defaults to 1 which means that we'll ask 796 for a minimum of 1 IO in the retrieval process from 797 the kernel. The IO retrieval will go on until we 798 hit the limit set by iodepth_low. If this variable is 799 set to 0, then fio will always check for completed 800 events before queuing more IO. This helps reduce 801 IO latency, at the cost of more retrieval system calls. 802 803 iodepth_low=int The low water mark indicating when to start filling 804 the queue again. Defaults to the same as iodepth, meaning 805 that fio will attempt to keep the queue full at all times. 806 If iodepth is set to eg 16 and iodepth_low is set to 4, then 807 after fio has filled the queue of 16 requests, it will let 808 the depth drain down to 4 before starting to fill it again. 809 810 direct=bool If value is true, use non-buffered io. This is usually 811 O_DIRECT. Note that ZFS on Solaris doesn't support direct io. 812 On Windows the synchronous ioengines don't support direct io. 813 814 atomic=bool If value is true, attempt to use atomic direct IO. Atomic 815 writes are guaranteed to be stable once acknowledged by 816 the operating system. Only Linux supports O_ATOMIC right 817 now. 818 819 buffered=bool If value is true, use buffered io. This is the opposite 820 of the 'direct' option. Defaults to true. 821 822 offset=int Start io at the given offset in the file. The data before 823 the given offset will not be touched. This effectively 824 caps the file size at real_size - offset. 825 826 offset_increment=int If this is provided, then the real offset becomes 827 offset + offset_increment * thread_number, where the thread 828 number is a counter that starts at 0 and is incremented for 829 each sub-job (i.e. when numjobs option is specified). This 830 option is useful if there are several jobs which are intended 831 to operate on a file in parallel disjoint segments, with 832 even spacing between the starting points. 833 834 number_ios=int Fio will normally perform IOs until it has exhausted the size 835 of the region set by size=, or if it exhaust the allocated 836 time (or hits an error condition). With this setting, the 837 range/size can be set independently of the number of IOs to 838 perform. When fio reaches this number, it will exit normally 839 and report status. Note that this does not extend the amount 840 of IO that will be done, it will only stop fio if this 841 condition is met before other end-of-job criteria. 842 843 fsync=int If writing to a file, issue a sync of the dirty data 844 for every number of blocks given. For example, if you give 845 32 as a parameter, fio will sync the file for every 32 846 writes issued. If fio is using non-buffered io, we may 847 not sync the file. The exception is the sg io engine, which 848 synchronizes the disk cache anyway. 849 850 fdatasync=int Like fsync= but uses fdatasync() to only sync data and not 851 metadata blocks. 852 In FreeBSD and Windows there is no fdatasync(), this falls back to 853 using fsync() 854 855 sync_file_range=str:val Use sync_file_range() for every 'val' number of 856 write operations. Fio will track range of writes that 857 have happened since the last sync_file_range() call. 'str' 858 can currently be one or more of: 859 860 wait_before SYNC_FILE_RANGE_WAIT_BEFORE 861 write SYNC_FILE_RANGE_WRITE 862 wait_after SYNC_FILE_RANGE_WAIT_AFTER 863 864 So if you do sync_file_range=wait_before,write:8, fio would 865 use SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE for 866 every 8 writes. Also see the sync_file_range(2) man page. 867 This option is Linux specific. 868 869 overwrite=bool If true, writes to a file will always overwrite existing 870 data. If the file doesn't already exist, it will be 871 created before the write phase begins. If the file exists 872 and is large enough for the specified write phase, nothing 873 will be done. 874 875 end_fsync=bool If true, fsync file contents when a write stage has completed. 876 877 fsync_on_close=bool If true, fio will fsync() a dirty file on close. 878 This differs from end_fsync in that it will happen on every 879 file close, not just at the end of the job. 880 881 rwmixread=int How large a percentage of the mix should be reads. 882 883 rwmixwrite=int How large a percentage of the mix should be writes. If both 884 rwmixread and rwmixwrite is given and the values do not add 885 up to 100%, the latter of the two will be used to override 886 the first. This may interfere with a given rate setting, 887 if fio is asked to limit reads or writes to a certain rate. 888 If that is the case, then the distribution may be skewed. 889 890 random_distribution=str:float By default, fio will use a completely uniform 891 random distribution when asked to perform random IO. Sometimes 892 it is useful to skew the distribution in specific ways, 893 ensuring that some parts of the data is more hot than others. 894 fio includes the following distribution models: 895 896 random Uniform random distribution 897 zipf Zipf distribution 898 pareto Pareto distribution 899 900 When using a zipf or pareto distribution, an input value 901 is also needed to define the access pattern. For zipf, this 902 is the zipf theta. For pareto, it's the pareto power. Fio 903 includes a test program, genzipf, that can be used visualize 904 what the given input values will yield in terms of hit rates. 905 If you wanted to use zipf with a theta of 1.2, you would use 906 random_distribution=zipf:1.2 as the option. If a non-uniform 907 model is used, fio will disable use of the random map. 908 909 percentage_random=int For a random workload, set how big a percentage should 910 be random. This defaults to 100%, in which case the workload 911 is fully random. It can be set from anywhere from 0 to 100. 912 Setting it to 0 would make the workload fully sequential. Any 913 setting in between will result in a random mix of sequential 914 and random IO, at the given percentages. It is possible to 915 set different values for reads, writes, and trim. To do so, 916 simply use a comma separated list. See blocksize. 917 918 norandommap Normally fio will cover every block of the file when doing 919 random IO. If this option is given, fio will just get a 920 new random offset without looking at past io history. This 921 means that some blocks may not be read or written, and that 922 some blocks may be read/written more than once. If this option 923 is used with verify= and multiple blocksizes (via bsrange=), 924 only intact blocks are verified, i.e., partially-overwritten 925 blocks are ignored. 926 927 softrandommap=bool See norandommap. If fio runs with the random block map 928 enabled and it fails to allocate the map, if this option is 929 set it will continue without a random block map. As coverage 930 will not be as complete as with random maps, this option is 931 disabled by default. 932 933 random_generator=str Fio supports the following engines for generating 934 IO offsets for random IO: 935 936 tausworthe Strong 2^88 cycle random number generator 937 lfsr Linear feedback shift register generator 938 939 Tausworthe is a strong random number generator, but it 940 requires tracking on the side if we want to ensure that 941 blocks are only read or written once. LFSR guarantees 942 that we never generate the same offset twice, and it's 943 also less computationally expensive. It's not a true 944 random generator, however, though for IO purposes it's 945 typically good enough. LFSR only works with single 946 block sizes, not with workloads that use multiple block 947 sizes. If used with such a workload, fio may read or write 948 some blocks multiple times. 949 950 nice=int Run the job with the given nice value. See man nice(2). 951 952 prio=int Set the io priority value of this job. Linux limits us to 953 a positive value between 0 and 7, with 0 being the highest. 954 See man ionice(1). 955 956 prioclass=int Set the io priority class. See man ionice(1). 957 958 thinktime=int Stall the job x microseconds after an io has completed before 959 issuing the next. May be used to simulate processing being 960 done by an application. See thinktime_blocks and 961 thinktime_spin. 962 963 thinktime_spin=int 964 Only valid if thinktime is set - pretend to spend CPU time 965 doing something with the data received, before falling back 966 to sleeping for the rest of the period specified by 967 thinktime. 968 969 thinktime_blocks=int 970 Only valid if thinktime is set - control how many blocks 971 to issue, before waiting 'thinktime' usecs. If not set, 972 defaults to 1 which will make fio wait 'thinktime' usecs 973 after every block. This effectively makes any queue depth 974 setting redundant, since no more than 1 IO will be queued 975 before we have to complete it and do our thinktime. In 976 other words, this setting effectively caps the queue depth 977 if the latter is larger. 978 979 rate=int Cap the bandwidth used by this job. The number is in bytes/sec, 980 the normal suffix rules apply. You can use rate=500k to limit 981 reads and writes to 500k each, or you can specify read and 982 writes separately. Using rate=1m,500k would limit reads to 983 1MB/sec and writes to 500KB/sec. Capping only reads or 984 writes can be done with rate=,500k or rate=500k,. The former 985 will only limit writes (to 500KB/sec), the latter will only 986 limit reads. 987 988 ratemin=int Tell fio to do whatever it can to maintain at least this 989 bandwidth. Failing to meet this requirement, will cause 990 the job to exit. The same format as rate is used for 991 read vs write separation. 992 993 rate_iops=int Cap the bandwidth to this number of IOPS. Basically the same 994 as rate, just specified independently of bandwidth. If the 995 job is given a block size range instead of a fixed value, 996 the smallest block size is used as the metric. The same format 997 as rate is used for read vs write separation. 998 999 rate_iops_min=int If fio doesn't meet this rate of IO, it will cause 1000 the job to exit. The same format as rate is used for read vs 1001 write separation. 1002 1003 latency_target=int If set, fio will attempt to find the max performance 1004 point that the given workload will run at while maintaining a 1005 latency below this target. The values is given in microseconds. 1006 See latency_window and latency_percentile 1007 1008 latency_window=int Used with latency_target to specify the sample window 1009 that the job is run at varying queue depths to test the 1010 performance. The value is given in microseconds. 1011 1012 latency_percentile=float The percentage of IOs that must fall within the 1013 criteria specified by latency_target and latency_window. If not 1014 set, this defaults to 100.0, meaning that all IOs must be equal 1015 or below to the value set by latency_target. 1016 1017 max_latency=int If set, fio will exit the job if it exceeds this maximum 1018 latency. It will exit with an ETIME error. 1019 1020 ratecycle=int Average bandwidth for 'rate' and 'ratemin' over this number 1021 of milliseconds. 1022 1023 cpumask=int Set the CPU affinity of this job. The parameter given is a 1024 bitmask of allowed CPU's the job may run on. So if you want 1025 the allowed CPUs to be 1 and 5, you would pass the decimal 1026 value of (1 << 1 | 1 << 5), or 34. See man 1027 sched_setaffinity(2). This may not work on all supported 1028 operating systems or kernel versions. This option doesn't 1029 work well for a higher CPU count than what you can store in 1030 an integer mask, so it can only control cpus 1-32. For 1031 boxes with larger CPU counts, use cpus_allowed. 1032 1033 cpus_allowed=str Controls the same options as cpumask, but it allows a text 1034 setting of the permitted CPUs instead. So to use CPUs 1 and 1035 5, you would specify cpus_allowed=1,5. This options also 1036 allows a range of CPUs. Say you wanted a binding to CPUs 1037 1, 5, and 8-15, you would set cpus_allowed=1,5,8-15. 1038 1039 cpus_allowed_policy=str Set the policy of how fio distributes the CPUs 1040 specified by cpus_allowed or cpumask. Two policies are 1041 supported: 1042 1043 shared All jobs will share the CPU set specified. 1044 split Each job will get a unique CPU from the CPU set. 1045 1046 'shared' is the default behaviour, if the option isn't 1047 specified. If split is specified, then fio will will assign 1048 one cpu per job. If not enough CPUs are given for the jobs 1049 listed, then fio will roundrobin the CPUs in the set. 1050 1051 numa_cpu_nodes=str Set this job running on spcified NUMA nodes' CPUs. The 1052 arguments allow comma delimited list of cpu numbers, 1053 A-B ranges, or 'all'. Note, to enable numa options support, 1054 fio must be built on a system with libnuma-dev(el) installed. 1055 1056 numa_mem_policy=str Set this job's memory policy and corresponding NUMA 1057 nodes. Format of the argements: 1058 <mode>[:<nodelist>] 1059 `mode' is one of the following memory policy: 1060 default, prefer, bind, interleave, local 1061 For `default' and `local' memory policy, no node is 1062 needed to be specified. 1063 For `prefer', only one node is allowed. 1064 For `bind' and `interleave', it allow comma delimited 1065 list of numbers, A-B ranges, or 'all'. 1066 1067 startdelay=time Start this job the specified number of seconds after fio 1068 has started. Only useful if the job file contains several 1069 jobs, and you want to delay starting some jobs to a certain 1070 time. 1071 1072 runtime=time Tell fio to terminate processing after the specified number 1073 of seconds. It can be quite hard to determine for how long 1074 a specified job will run, so this parameter is handy to 1075 cap the total runtime to a given time. 1076 1077 time_based If set, fio will run for the duration of the runtime 1078 specified even if the file(s) are completely read or 1079 written. It will simply loop over the same workload 1080 as many times as the runtime allows. 1081 1082 ramp_time=time If set, fio will run the specified workload for this amount 1083 of time before logging any performance numbers. Useful for 1084 letting performance settle before logging results, thus 1085 minimizing the runtime required for stable results. Note 1086 that the ramp_time is considered lead in time for a job, 1087 thus it will increase the total runtime if a special timeout 1088 or runtime is specified. 1089 1090 invalidate=bool Invalidate the buffer/page cache parts for this file prior 1091 to starting io. Defaults to true. 1092 1093 sync=bool Use sync io for buffered writes. For the majority of the 1094 io engines, this means using O_SYNC. 1095 1096 iomem=str 1097 mem=str Fio can use various types of memory as the io unit buffer. 1098 The allowed values are: 1099 1100 malloc Use memory from malloc(3) as the buffers. 1101 1102 shm Use shared memory as the buffers. Allocated 1103 through shmget(2). 1104 1105 shmhuge Same as shm, but use huge pages as backing. 1106 1107 mmap Use mmap to allocate buffers. May either be 1108 anonymous memory, or can be file backed if 1109 a filename is given after the option. The 1110 format is mem=mmap:/path/to/file. 1111 1112 mmaphuge Use a memory mapped huge file as the buffer 1113 backing. Append filename after mmaphuge, ala 1114 mem=mmaphuge:/hugetlbfs/file 1115 1116 The area allocated is a function of the maximum allowed 1117 bs size for the job, multiplied by the io depth given. Note 1118 that for shmhuge and mmaphuge to work, the system must have 1119 free huge pages allocated. This can normally be checked 1120 and set by reading/writing /proc/sys/vm/nr_hugepages on a 1121 Linux system. Fio assumes a huge page is 4MB in size. So 1122 to calculate the number of huge pages you need for a given 1123 job file, add up the io depth of all jobs (normally one unless 1124 iodepth= is used) and multiply by the maximum bs set. Then 1125 divide that number by the huge page size. You can see the 1126 size of the huge pages in /proc/meminfo. If no huge pages 1127 are allocated by having a non-zero number in nr_hugepages, 1128 using mmaphuge or shmhuge will fail. Also see hugepage-size. 1129 1130 mmaphuge also needs to have hugetlbfs mounted and the file 1131 location should point there. So if it's mounted in /huge, 1132 you would use mem=mmaphuge:/huge/somefile. 1133 1134 iomem_align=int This indiciates the memory alignment of the IO memory buffers. 1135 Note that the given alignment is applied to the first IO unit 1136 buffer, if using iodepth the alignment of the following buffers 1137 are given by the bs used. In other words, if using a bs that is 1138 a multiple of the page sized in the system, all buffers will 1139 be aligned to this value. If using a bs that is not page 1140 aligned, the alignment of subsequent IO memory buffers is the 1141 sum of the iomem_align and bs used. 1142 1143 hugepage-size=int 1144 Defines the size of a huge page. Must at least be equal 1145 to the system setting, see /proc/meminfo. Defaults to 4MB. 1146 Should probably always be a multiple of megabytes, so using 1147 hugepage-size=Xm is the preferred way to set this to avoid 1148 setting a non-pow-2 bad value. 1149 1150 exitall When one job finishes, terminate the rest. The default is 1151 to wait for each job to finish, sometimes that is not the 1152 desired action. 1153 1154 bwavgtime=int Average the calculated bandwidth over the given time. Value 1155 is specified in milliseconds. 1156 1157 iopsavgtime=int Average the calculated IOPS over the given time. Value 1158 is specified in milliseconds. 1159 1160 create_serialize=bool If true, serialize the file creating for the jobs. 1161 This may be handy to avoid interleaving of data 1162 files, which may greatly depend on the filesystem 1163 used and even the number of processors in the system. 1164 1165 create_fsync=bool fsync the data file after creation. This is the 1166 default. 1167 1168 create_on_open=bool Don't pre-setup the files for IO, just create open() 1169 when it's time to do IO to that file. 1170 1171 create_only=bool If true, fio will only run the setup phase of the job. 1172 If files need to be laid out or updated on disk, only 1173 that will be done. The actual job contents are not 1174 executed. 1175 1176 pre_read=bool If this is given, files will be pre-read into memory before 1177 starting the given IO operation. This will also clear 1178 the 'invalidate' flag, since it is pointless to pre-read 1179 and then drop the cache. This will only work for IO engines 1180 that are seekable, since they allow you to read the same data 1181 multiple times. Thus it will not work on eg network or splice 1182 IO. 1183 1184 unlink=bool Unlink the job files when done. Not the default, as repeated 1185 runs of that job would then waste time recreating the file 1186 set again and again. 1187 1188 loops=int Run the specified number of iterations of this job. Used 1189 to repeat the same workload a given number of times. Defaults 1190 to 1. 1191 1192 verify_only Do not perform specified workload---only verify data still 1193 matches previous invocation of this workload. This option 1194 allows one to check data multiple times at a later date 1195 without overwriting it. This option makes sense only for 1196 workloads that write data, and does not support workloads 1197 with the time_based option set. 1198 1199 do_verify=bool Run the verify phase after a write phase. Only makes sense if 1200 verify is set. Defaults to 1. 1201 1202 verify=str If writing to a file, fio can verify the file contents 1203 after each iteration of the job. The allowed values are: 1204 1205 md5 Use an md5 sum of the data area and store 1206 it in the header of each block. 1207 1208 crc64 Use an experimental crc64 sum of the data 1209 area and store it in the header of each 1210 block. 1211 1212 crc32c Use a crc32c sum of the data area and store 1213 it in the header of each block. 1214 1215 crc32c-intel Use hardware assisted crc32c calcuation 1216 provided on SSE4.2 enabled processors. Falls 1217 back to regular software crc32c, if not 1218 supported by the system. 1219 1220 crc32 Use a crc32 sum of the data area and store 1221 it in the header of each block. 1222 1223 crc16 Use a crc16 sum of the data area and store 1224 it in the header of each block. 1225 1226 crc7 Use a crc7 sum of the data area and store 1227 it in the header of each block. 1228 1229 xxhash Use xxhash as the checksum function. Generally 1230 the fastest software checksum that fio 1231 supports. 1232 1233 sha512 Use sha512 as the checksum function. 1234 1235 sha256 Use sha256 as the checksum function. 1236 1237 sha1 Use optimized sha1 as the checksum function. 1238 1239 meta Write extra information about each io 1240 (timestamp, block number etc.). The block 1241 number is verified. The io sequence number is 1242 verified for workloads that write data. 1243 See also verify_pattern. 1244 1245 null Only pretend to verify. Useful for testing 1246 internals with ioengine=null, not for much 1247 else. 1248 1249 This option can be used for repeated burn-in tests of a 1250 system to make sure that the written data is also 1251 correctly read back. If the data direction given is 1252 a read or random read, fio will assume that it should 1253 verify a previously written file. If the data direction 1254 includes any form of write, the verify will be of the 1255 newly written data. 1256 1257 verifysort=bool If set, fio will sort written verify blocks when it deems 1258 it faster to read them back in a sorted manner. This is 1259 often the case when overwriting an existing file, since 1260 the blocks are already laid out in the file system. You 1261 can ignore this option unless doing huge amounts of really 1262 fast IO where the red-black tree sorting CPU time becomes 1263 significant. 1264 1265 verify_offset=int Swap the verification header with data somewhere else 1266 in the block before writing. Its swapped back before 1267 verifying. 1268 1269 verify_interval=int Write the verification header at a finer granularity 1270 than the blocksize. It will be written for chunks the 1271 size of header_interval. blocksize should divide this 1272 evenly. 1273 1274 verify_pattern=str If set, fio will fill the io buffers with this 1275 pattern. Fio defaults to filling with totally random 1276 bytes, but sometimes it's interesting to fill with a known 1277 pattern for io verification purposes. Depending on the 1278 width of the pattern, fio will fill 1/2/3/4 bytes of the 1279 buffer at the time(it can be either a decimal or a hex number). 1280 The verify_pattern if larger than a 32-bit quantity has to 1281 be a hex number that starts with either "0x" or "0X". Use 1282 with verify=meta. 1283 1284 verify_fatal=bool Normally fio will keep checking the entire contents 1285 before quitting on a block verification failure. If this 1286 option is set, fio will exit the job on the first observed 1287 failure. 1288 1289 verify_dump=bool If set, dump the contents of both the original data 1290 block and the data block we read off disk to files. This 1291 allows later analysis to inspect just what kind of data 1292 corruption occurred. Off by default. 1293 1294 verify_async=int Fio will normally verify IO inline from the submitting 1295 thread. This option takes an integer describing how many 1296 async offload threads to create for IO verification instead, 1297 causing fio to offload the duty of verifying IO contents 1298 to one or more separate threads. If using this offload 1299 option, even sync IO engines can benefit from using an 1300 iodepth setting higher than 1, as it allows them to have 1301 IO in flight while verifies are running. 1302 1303 verify_async_cpus=str Tell fio to set the given CPU affinity on the 1304 async IO verification threads. See cpus_allowed for the 1305 format used. 1306 1307 verify_backlog=int Fio will normally verify the written contents of a 1308 job that utilizes verify once that job has completed. In 1309 other words, everything is written then everything is read 1310 back and verified. You may want to verify continually 1311 instead for a variety of reasons. Fio stores the meta data 1312 associated with an IO block in memory, so for large 1313 verify workloads, quite a bit of memory would be used up 1314 holding this meta data. If this option is enabled, fio 1315 will write only N blocks before verifying these blocks. 1316 1317 verify_backlog_batch=int Control how many blocks fio will verify 1318 if verify_backlog is set. If not set, will default to 1319 the value of verify_backlog (meaning the entire queue 1320 is read back and verified). If verify_backlog_batch is 1321 less than verify_backlog then not all blocks will be verified, 1322 if verify_backlog_batch is larger than verify_backlog, some 1323 blocks will be verified more than once. 1324 1325 verify_state_save=bool When a job exits during the write phase of a verify 1326 workload, save its current state. This allows fio to replay 1327 up until that point, if the verify state is loaded for the 1328 verify read phase. The format of the filename is, roughly, 1329 <type>-<jobname>-<jobindex>-verify.state. <type> is "local" 1330 for a local run, "sock" for a client/server socket connection, 1331 and "ip" (192.168.0.1, for instance) for a networked 1332 client/server connection. 1333 1334 verify_state_load=bool If a verify termination trigger was used, fio stores 1335 the current write state of each thread. This can be used at 1336 verification time so that fio knows how far it should verify. 1337 Without this information, fio will run a full verification 1338 pass, according to the settings in the job file used. 1339 1340 stonewall 1341 wait_for_previous Wait for preceding jobs in the job file to exit, before 1342 starting this one. Can be used to insert serialization 1343 points in the job file. A stone wall also implies starting 1344 a new reporting group. 1345 1346 new_group Start a new reporting group. See: group_reporting. 1347 1348 numjobs=int Create the specified number of clones of this job. May be 1349 used to setup a larger number of threads/processes doing 1350 the same thing. Each thread is reported separately; to see 1351 statistics for all clones as a whole, use group_reporting in 1352 conjunction with new_group. 1353 1354 group_reporting It may sometimes be interesting to display statistics for 1355 groups of jobs as a whole instead of for each individual job. 1356 This is especially true if 'numjobs' is used; looking at 1357 individual thread/process output quickly becomes unwieldy. 1358 To see the final report per-group instead of per-job, use 1359 'group_reporting'. Jobs in a file will be part of the same 1360 reporting group, unless if separated by a stonewall, or by 1361 using 'new_group'. 1362 1363 thread fio defaults to forking jobs, however if this option is 1364 given, fio will use pthread_create(3) to create threads 1365 instead. 1366 1367 zonesize=int Divide a file into zones of the specified size. See zoneskip. 1368 1369 zoneskip=int Skip the specified number of bytes when zonesize data has 1370 been read. The two zone options can be used to only do 1371 io on zones of a file. 1372 1373 write_iolog=str Write the issued io patterns to the specified file. See 1374 read_iolog. Specify a separate file for each job, otherwise 1375 the iologs will be interspersed and the file may be corrupt. 1376 1377 read_iolog=str Open an iolog with the specified file name and replay the 1378 io patterns it contains. This can be used to store a 1379 workload and replay it sometime later. The iolog given 1380 may also be a blktrace binary file, which allows fio 1381 to replay a workload captured by blktrace. See blktrace 1382 for how to capture such logging data. For blktrace replay, 1383 the file needs to be turned into a blkparse binary data 1384 file first (blkparse <device> -o /dev/null -d file_for_fio.bin). 1385 1386 replay_no_stall=int When replaying I/O with read_iolog the default behavior 1387 is to attempt to respect the time stamps within the log and 1388 replay them with the appropriate delay between IOPS. By 1389 setting this variable fio will not respect the timestamps and 1390 attempt to replay them as fast as possible while still 1391 respecting ordering. The result is the same I/O pattern to a 1392 given device, but different timings. 1393 1394 replay_redirect=str While replaying I/O patterns using read_iolog the 1395 default behavior is to replay the IOPS onto the major/minor 1396 device that each IOP was recorded from. This is sometimes 1397 undesirable because on a different machine those major/minor 1398 numbers can map to a different device. Changing hardware on 1399 the same system can also result in a different major/minor 1400 mapping. Replay_redirect causes all IOPS to be replayed onto 1401 the single specified device regardless of the device it was 1402 recorded from. i.e. replay_redirect=/dev/sdc would cause all 1403 IO in the blktrace to be replayed onto /dev/sdc. This means 1404 multiple devices will be replayed onto a single, if the trace 1405 contains multiple devices. If you want multiple devices to be 1406 replayed concurrently to multiple redirected devices you must 1407 blkparse your trace into separate traces and replay them with 1408 independent fio invocations. Unfortuantely this also breaks 1409 the strict time ordering between multiple device accesses. 1410 1411 write_bw_log=str If given, write a bandwidth log of the jobs in this job 1412 file. Can be used to store data of the bandwidth of the 1413 jobs in their lifetime. The included fio_generate_plots 1414 script uses gnuplot to turn these text files into nice 1415 graphs. See write_lat_log for behaviour of given 1416 filename. For this option, the suffix is _bw.x.log, where 1417 x is the index of the job (1..N, where N is the number of 1418 jobs). 1419 1420 write_lat_log=str Same as write_bw_log, except that this option stores io 1421 submission, completion, and total latencies instead. If no 1422 filename is given with this option, the default filename of 1423 "jobname_type.log" is used. Even if the filename is given, 1424 fio will still append the type of log. So if one specifies 1425 1426 write_lat_log=foo 1427 1428 The actual log names will be foo_slat.x.log, foo_clat.x.log, 1429 and foo_lat.x.log, where x is the index of the job (1..N, 1430 where N is the number of jobs). This helps fio_generate_plot 1431 fine the logs automatically. 1432 1433 write_iops_log=str Same as write_bw_log, but writes IOPS. If no filename is 1434 given with this option, the default filename of 1435 "jobname_type.x.log" is used,where x is the index of the job 1436 (1..N, where N is the number of jobs). Even if the filename 1437 is given, fio will still append the type of log. 1438 1439 log_avg_msec=int By default, fio will log an entry in the iops, latency, 1440 or bw log for every IO that completes. When writing to the 1441 disk log, that can quickly grow to a very large size. Setting 1442 this option makes fio average the each log entry over the 1443 specified period of time, reducing the resolution of the log. 1444 Defaults to 0. 1445 1446 log_offset=int If this is set, the iolog options will include the byte 1447 offset for the IO entry as well as the other data values. 1448 1449 log_compression=int If this is set, fio will compress the IO logs as 1450 it goes, to keep the memory footprint lower. When a log 1451 reaches the specified size, that chunk is removed and 1452 compressed in the background. Given that IO logs are 1453 fairly highly compressible, this yields a nice memory 1454 savings for longer runs. The downside is that the 1455 compression will consume some background CPU cycles, so 1456 it may impact the run. This, however, is also true if 1457 the logging ends up consuming most of the system memory. 1458 So pick your poison. The IO logs are saved normally at the 1459 end of a run, by decompressing the chunks and storing them 1460 in the specified log file. This feature depends on the 1461 availability of zlib. 1462 1463 log_store_compressed=bool If set, and log_compression is also set, 1464 fio will store the log files in a compressed format. They 1465 can be decompressed with fio, using the --inflate-log 1466 command line parameter. The files will be stored with a 1467 .fz suffix. 1468 1469 lockmem=int Pin down the specified amount of memory with mlock(2). Can 1470 potentially be used instead of removing memory or booting 1471 with less memory to simulate a smaller amount of memory. 1472 The amount specified is per worker. 1473 1474 exec_prerun=str Before running this job, issue the command specified 1475 through system(3). Output is redirected in a file called 1476 jobname.prerun.txt. 1477 1478 exec_postrun=str After the job completes, issue the command specified 1479 though system(3). Output is redirected in a file called 1480 jobname.postrun.txt. 1481 1482 ioscheduler=str Attempt to switch the device hosting the file to the specified 1483 io scheduler before running. 1484 1485 disk_util=bool Generate disk utilization statistics, if the platform 1486 supports it. Defaults to on. 1487 1488 disable_lat=bool Disable measurements of total latency numbers. Useful 1489 only for cutting back the number of calls to gettimeofday, 1490 as that does impact performance at really high IOPS rates. 1491 Note that to really get rid of a large amount of these 1492 calls, this option must be used with disable_slat and 1493 disable_bw as well. 1494 1495 disable_clat=bool Disable measurements of completion latency numbers. See 1496 disable_lat. 1497 1498 disable_slat=bool Disable measurements of submission latency numbers. See 1499 disable_slat. 1500 1501 disable_bw=bool Disable measurements of throughput/bandwidth numbers. See 1502 disable_lat. 1503 1504 clat_percentiles=bool Enable the reporting of percentiles of 1505 completion latencies. 1506 1507 percentile_list=float_list Overwrite the default list of percentiles 1508 for completion latencies. Each number is a floating 1509 number in the range (0,100], and the maximum length of 1510 the list is 20. Use ':' to separate the numbers, and 1511 list the numbers in ascending order. For example, 1512 --percentile_list=99.5:99.9 will cause fio to report 1513 the values of completion latency below which 99.5% and 1514 99.9% of the observed latencies fell, respectively. 1515 1516 clocksource=str Use the given clocksource as the base of timing. The 1517 supported options are: 1518 1519 gettimeofday gettimeofday(2) 1520 1521 clock_gettime clock_gettime(2) 1522 1523 cpu Internal CPU clock source 1524 1525 cpu is the preferred clocksource if it is reliable, as it 1526 is very fast (and fio is heavy on time calls). Fio will 1527 automatically use this clocksource if it's supported and 1528 considered reliable on the system it is running on, unless 1529 another clocksource is specifically set. For x86/x86-64 CPUs, 1530 this means supporting TSC Invariant. 1531 1532 gtod_reduce=bool Enable all of the gettimeofday() reducing options 1533 (disable_clat, disable_slat, disable_bw) plus reduce 1534 precision of the timeout somewhat to really shrink 1535 the gettimeofday() call count. With this option enabled, 1536 we only do about 0.4% of the gtod() calls we would have 1537 done if all time keeping was enabled. 1538 1539 gtod_cpu=int Sometimes it's cheaper to dedicate a single thread of 1540 execution to just getting the current time. Fio (and 1541 databases, for instance) are very intensive on gettimeofday() 1542 calls. With this option, you can set one CPU aside for 1543 doing nothing but logging current time to a shared memory 1544 location. Then the other threads/processes that run IO 1545 workloads need only copy that segment, instead of entering 1546 the kernel with a gettimeofday() call. The CPU set aside 1547 for doing these time calls will be excluded from other 1548 uses. Fio will manually clear it from the CPU mask of other 1549 jobs. 1550 1551 continue_on_error=str Normally fio will exit the job on the first observed 1552 failure. If this option is set, fio will continue the job when 1553 there is a 'non-fatal error' (EIO or EILSEQ) until the runtime 1554 is exceeded or the I/O size specified is completed. If this 1555 option is used, there are two more stats that are appended, 1556 the total error count and the first error. The error field 1557 given in the stats is the first error that was hit during the 1558 run. 1559 1560 The allowed values are: 1561 1562 none Exit on any IO or verify errors. 1563 1564 read Continue on read errors, exit on all others. 1565 1566 write Continue on write errors, exit on all others. 1567 1568 io Continue on any IO error, exit on all others. 1569 1570 verify Continue on verify errors, exit on all others. 1571 1572 all Continue on all errors. 1573 1574 0 Backward-compatible alias for 'none'. 1575 1576 1 Backward-compatible alias for 'all'. 1577 1578 ignore_error=str Sometimes you want to ignore some errors during test 1579 in that case you can specify error list for each error type. 1580 ignore_error=READ_ERR_LIST,WRITE_ERR_LIST,VERIFY_ERR_LIST 1581 errors for given error type is separated with ':'. Error 1582 may be symbol ('ENOSPC', 'ENOMEM') or integer. 1583 Example: 1584 ignore_error=EAGAIN,ENOSPC:122 1585 This option will ignore EAGAIN from READ, and ENOSPC and 1586 122(EDQUOT) from WRITE. 1587 1588 error_dump=bool If set dump every error even if it is non fatal, true 1589 by default. If disabled only fatal error will be dumped 1590 1591 cgroup=str Add job to this control group. If it doesn't exist, it will 1592 be created. The system must have a mounted cgroup blkio 1593 mount point for this to work. If your system doesn't have it 1594 mounted, you can do so with: 1595 1596 # mount -t cgroup -o blkio none /cgroup 1597 1598 cgroup_weight=int Set the weight of the cgroup to this value. See 1599 the documentation that comes with the kernel, allowed values 1600 are in the range of 100..1000. 1601 1602 cgroup_nodelete=bool Normally fio will delete the cgroups it has created after 1603 the job completion. To override this behavior and to leave 1604 cgroups around after the job completion, set cgroup_nodelete=1. 1605 This can be useful if one wants to inspect various cgroup 1606 files after job completion. Default: false 1607 1608 uid=int Instead of running as the invoking user, set the user ID to 1609 this value before the thread/process does any work. 1610 1611 gid=int Set group ID, see uid. 1612 1613 flow_id=int The ID of the flow. If not specified, it defaults to being a 1614 global flow. See flow. 1615 1616 flow=int Weight in token-based flow control. If this value is used, then 1617 there is a 'flow counter' which is used to regulate the 1618 proportion of activity between two or more jobs. fio attempts 1619 to keep this flow counter near zero. The 'flow' parameter 1620 stands for how much should be added or subtracted to the flow 1621 counter on each iteration of the main I/O loop. That is, if 1622 one job has flow=8 and another job has flow=-1, then there 1623 will be a roughly 1:8 ratio in how much one runs vs the other. 1624 1625 flow_watermark=int The maximum value that the absolute value of the flow 1626 counter is allowed to reach before the job must wait for a 1627 lower value of the counter. 1628 1629 flow_sleep=int The period of time, in microseconds, to wait after the flow 1630 watermark has been exceeded before retrying operations 1631 1632 In addition, there are some parameters which are only valid when a specific 1633 ioengine is in use. These are used identically to normal parameters, with the 1634 caveat that when used on the command line, they must come after the ioengine 1635 that defines them is selected. 1636 1637 [libaio] userspace_reap Normally, with the libaio engine in use, fio will use 1638 the io_getevents system call to reap newly returned events. 1639 With this flag turned on, the AIO ring will be read directly 1640 from user-space to reap events. The reaping mode is only 1641 enabled when polling for a minimum of 0 events (eg when 1642 iodepth_batch_complete=0). 1643 1644 [cpu] cpuload=int Attempt to use the specified percentage of CPU cycles. 1645 1646 [cpu] cpuchunks=int Split the load into cycles of the given time. In 1647 microseconds. 1648 1649 [cpu] exit_on_io_done=bool Detect when IO threads are done, then exit. 1650 1651 [netsplice] hostname=str 1652 [net] hostname=str The host name or IP address to use for TCP or UDP based IO. 1653 If the job is a TCP listener or UDP reader, the hostname is not 1654 used and must be omitted unless it is a valid UDP multicast 1655 address. 1656 1657 [netsplice] port=int 1658 [net] port=int The TCP or UDP port to bind to or connect to. If this is used 1659 with numjobs to spawn multiple instances of the same job type, then this will 1660 be the starting port number since fio will use a range of ports. 1661 1662 [netsplice] interface=str 1663 [net] interface=str The IP address of the network interface used to send or 1664 receive UDP multicast 1665 1666 [netsplice] ttl=int 1667 [net] ttl=int Time-to-live value for outgoing UDP multicast packets. 1668 Default: 1 1669 1670 [netsplice] nodelay=bool 1671 [net] nodelay=bool Set TCP_NODELAY on TCP connections. 1672 1673 [netsplice] protocol=str 1674 [netsplice] proto=str 1675 [net] protocol=str 1676 [net] proto=str The network protocol to use. Accepted values are: 1677 1678 tcp Transmission control protocol 1679 tcpv6 Transmission control protocol V6 1680 udp User datagram protocol 1681 udpv6 User datagram protocol V6 1682 unix UNIX domain socket 1683 1684 When the protocol is TCP or UDP, the port must also be given, 1685 as well as the hostname if the job is a TCP listener or UDP 1686 reader. For unix sockets, the normal filename option should be 1687 used and the port is invalid. 1688 1689 [net] listen For TCP network connections, tell fio to listen for incoming 1690 connections rather than initiating an outgoing connection. The 1691 hostname must be omitted if this option is used. 1692 1693 [net] pingpong Normaly a network writer will just continue writing data, and 1694 a network reader will just consume packages. If pingpong=1 1695 is set, a writer will send its normal payload to the reader, 1696 then wait for the reader to send the same payload back. This 1697 allows fio to measure network latencies. The submission 1698 and completion latencies then measure local time spent 1699 sending or receiving, and the completion latency measures 1700 how long it took for the other end to receive and send back. 1701 For UDP multicast traffic pingpong=1 should only be set for a 1702 single reader when multiple readers are listening to the same 1703 address. 1704 1705 [net] window_size Set the desired socket buffer size for the connection. 1706 1707 [net] mss Set the TCP maximum segment size (TCP_MAXSEG). 1708 1709 [e4defrag] donorname=str 1710 File will be used as a block donor(swap extents between files) 1711 [e4defrag] inplace=int 1712 Configure donor file blocks allocation strategy 1713 0(default): Preallocate donor's file on init 1714 1 : allocate space immidietly inside defragment event, 1715 and free right after event 1716 1717 1718 1719 6.0 Interpreting the output 1720 --------------------------- 1721 1722 fio spits out a lot of output. While running, fio will display the 1723 status of the jobs created. An example of that would be: 1724 1725 Threads: 1: [_r] [24.8% done] [ 13509/ 8334 kb/s] [eta 00h:01m:31s] 1726 1727 The characters inside the square brackets denote the current status of 1728 each thread. The possible values (in typical life cycle order) are: 1729 1730 Idle Run 1731 ---- --- 1732 P Thread setup, but not started. 1733 C Thread created. 1734 I Thread initialized, waiting or generating necessary data. 1735 p Thread running pre-reading file(s). 1736 R Running, doing sequential reads. 1737 r Running, doing random reads. 1738 W Running, doing sequential writes. 1739 w Running, doing random writes. 1740 M Running, doing mixed sequential reads/writes. 1741 m Running, doing mixed random reads/writes. 1742 F Running, currently waiting for fsync() 1743 f Running, finishing up (writing IO logs, etc) 1744 V Running, doing verification of written data. 1745 E Thread exited, not reaped by main thread yet. 1746 _ Thread reaped, or 1747 X Thread reaped, exited with an error. 1748 K Thread reaped, exited due to signal. 1749 1750 Fio will condense the thread string as not to take up more space on the 1751 command line as is needed. For instance, if you have 10 readers and 10 1752 writers running, the output would look like this: 1753 1754 Jobs: 20 (f=20): [R(10),W(10)] [4.0% done] [2103MB/0KB/0KB /s] [538K/0/0 iops] [eta 57m:36s] 1755 1756 Fio will still maintain the ordering, though. So the above means that jobs 1757 1..10 are readers, and 11..20 are writers. 1758 1759 The other values are fairly self explanatory - number of threads 1760 currently running and doing io, rate of io since last check (read speed 1761 listed first, then write speed), and the estimated completion percentage 1762 and time for the running group. It's impossible to estimate runtime of 1763 the following groups (if any). Note that the string is displayed in order, 1764 so it's possible to tell which of the jobs are currently doing what. The 1765 first character is the first job defined in the job file, and so forth. 1766 1767 When fio is done (or interrupted by ctrl-c), it will show the data for 1768 each thread, group of threads, and disks in that order. For each data 1769 direction, the output looks like: 1770 1771 Client1 (g=0): err= 0: 1772 write: io= 32MB, bw= 666KB/s, iops=89 , runt= 50320msec 1773 slat (msec): min= 0, max= 136, avg= 0.03, stdev= 1.92 1774 clat (msec): min= 0, max= 631, avg=48.50, stdev=86.82 1775 bw (KB/s) : min= 0, max= 1196, per=51.00%, avg=664.02, stdev=681.68 1776 cpu : usr=1.49%, sys=0.25%, ctx=7969, majf=0, minf=17 1777 IO depths : 1=0.1%, 2=0.3%, 4=0.5%, 8=99.0%, 16=0.0%, 32=0.0%, >32=0.0% 1778 submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% 1779 complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% 1780 issued r/w: total=0/32768, short=0/0 1781 lat (msec): 2=1.6%, 4=0.0%, 10=3.2%, 20=12.8%, 50=38.4%, 100=24.8%, 1782 lat (msec): 250=15.2%, 500=0.0%, 750=0.0%, 1000=0.0%, >=2048=0.0% 1783 1784 The client number is printed, along with the group id and error of that 1785 thread. Below is the io statistics, here for writes. In the order listed, 1786 they denote: 1787 1788 io= Number of megabytes io performed 1789 bw= Average bandwidth rate 1790 iops= Average IOs performed per second 1791 runt= The runtime of that thread 1792 slat= Submission latency (avg being the average, stdev being the 1793 standard deviation). This is the time it took to submit 1794 the io. For sync io, the slat is really the completion 1795 latency, since queue/complete is one operation there. This 1796 value can be in milliseconds or microseconds, fio will choose 1797 the most appropriate base and print that. In the example 1798 above, milliseconds is the best scale. Note: in --minimal mode 1799 latencies are always expressed in microseconds. 1800 clat= Completion latency. Same names as slat, this denotes the 1801 time from submission to completion of the io pieces. For 1802 sync io, clat will usually be equal (or very close) to 0, 1803 as the time from submit to complete is basically just 1804 CPU time (io has already been done, see slat explanation). 1805 bw= Bandwidth. Same names as the xlat stats, but also includes 1806 an approximate percentage of total aggregate bandwidth 1807 this thread received in this group. This last value is 1808 only really useful if the threads in this group are on the 1809 same disk, since they are then competing for disk access. 1810 cpu= CPU usage. User and system time, along with the number 1811 of context switches this thread went through, usage of 1812 system and user time, and finally the number of major 1813 and minor page faults. 1814 IO depths= The distribution of io depths over the job life time. The 1815 numbers are divided into powers of 2, so for example the 1816 16= entries includes depths up to that value but higher 1817 than the previous entry. In other words, it covers the 1818 range from 16 to 31. 1819 IO submit= How many pieces of IO were submitting in a single submit 1820 call. Each entry denotes that amount and below, until 1821 the previous entry - eg, 8=100% mean that we submitted 1822 anywhere in between 5-8 ios per submit call. 1823 IO complete= Like the above submit number, but for completions instead. 1824 IO issued= The number of read/write requests issued, and how many 1825 of them were short. 1826 IO latencies= The distribution of IO completion latencies. This is the 1827 time from when IO leaves fio and when it gets completed. 1828 The numbers follow the same pattern as the IO depths, 1829 meaning that 2=1.6% means that 1.6% of the IO completed 1830 within 2 msecs, 20=12.8% means that 12.8% of the IO 1831 took more than 10 msecs, but less than (or equal to) 20 msecs. 1832 1833 After each client has been listed, the group statistics are printed. They 1834 will look like this: 1835 1836 Run status group 0 (all jobs): 1837 READ: io=64MB, aggrb=22178, minb=11355, maxb=11814, mint=2840msec, maxt=2955msec 1838 WRITE: io=64MB, aggrb=1302, minb=666, maxb=669, mint=50093msec, maxt=50320msec 1839 1840 For each data direction, it prints: 1841 1842 io= Number of megabytes io performed. 1843 aggrb= Aggregate bandwidth of threads in this group. 1844 minb= The minimum average bandwidth a thread saw. 1845 maxb= The maximum average bandwidth a thread saw. 1846 mint= The smallest runtime of the threads in that group. 1847 maxt= The longest runtime of the threads in that group. 1848 1849 And finally, the disk statistics are printed. They will look like this: 1850 1851 Disk stats (read/write): 1852 sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00% 1853 1854 Each value is printed for both reads and writes, with reads first. The 1855 numbers denote: 1856 1857 ios= Number of ios performed by all groups. 1858 merge= Number of merges io the io scheduler. 1859 ticks= Number of ticks we kept the disk busy. 1860 io_queue= Total time spent in the disk queue. 1861 util= The disk utilization. A value of 100% means we kept the disk 1862 busy constantly, 50% would be a disk idling half of the time. 1863 1864 It is also possible to get fio to dump the current output while it is 1865 running, without terminating the job. To do that, send fio the USR1 signal. 1866 You can also get regularly timed dumps by using the --status-interval 1867 parameter, or by creating a file in /tmp named fio-dump-status. If fio 1868 sees this file, it will unlink it and dump the current output status. 1869 1870 1871 7.0 Terse output 1872 ---------------- 1873 1874 For scripted usage where you typically want to generate tables or graphs 1875 of the results, fio can output the results in a semicolon separated format. 1876 The format is one long line of values, such as: 1877 1878 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% 1879 A description of this job goes here. 1880 1881 The job description (if provided) follows on a second line. 1882 1883 To enable terse output, use the --minimal command line option. The first 1884 value is the version of the terse output format. If the output has to 1885 be changed for some reason, this number will be incremented by 1 to 1886 signify that change. 1887 1888 Split up, the format is as follows: 1889 1890 terse version, fio version, jobname, groupid, error 1891 READ status: 1892 Total IO (KB), bandwidth (KB/sec), IOPS, runtime (msec) 1893 Submission latency: min, max, mean, deviation (usec) 1894 Completion latency: min, max, mean, deviation (usec) 1895 Completion latency percentiles: 20 fields (see below) 1896 Total latency: min, max, mean, deviation (usec) 1897 Bw (KB/s): min, max, aggregate percentage of total, mean, deviation 1898 WRITE status: 1899 Total IO (KB), bandwidth (KB/sec), IOPS, runtime (msec) 1900 Submission latency: min, max, mean, deviation (usec) 1901 Completion latency: min, max, mean, deviation (usec) 1902 Completion latency percentiles: 20 fields (see below) 1903 Total latency: min, max, mean, deviation (usec) 1904 Bw (KB/s): min, max, aggregate percentage of total, mean, deviation 1905 CPU usage: user, system, context switches, major faults, minor faults 1906 IO depths: <=1, 2, 4, 8, 16, 32, >=64 1907 IO latencies microseconds: <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000 1908 IO latencies milliseconds: <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, 2000, >=2000 1909 Disk utilization: Disk name, Read ios, write ios, 1910 Read merges, write merges, 1911 Read ticks, write ticks, 1912 Time spent in queue, disk utilization percentage 1913 Additional Info (dependent on continue_on_error, default off): total # errors, first error code 1914 1915 Additional Info (dependent on description being set): Text description 1916 1917 Completion latency percentiles can be a grouping of up to 20 sets, so 1918 for the terse output fio writes all of them. Each field will look like this: 1919 1920 1.00%=6112 1921 1922 which is the Xth percentile, and the usec latency associated with it. 1923 1924 For disk utilization, all disks used by fio are shown. So for each disk 1925 there will be a disk utilization section. 1926 1927 1928 8.0 Trace file format 1929 --------------------- 1930 There are two trace file format that you can encounter. The older (v1) format 1931 is unsupported since version 1.20-rc3 (March 2008). It will still be described 1932 below in case that you get an old trace and want to understand it. 1933 1934 In any case the trace is a simple text file with a single action per line. 1935 1936 1937 8.1 Trace file format v1 1938 ------------------------ 1939 Each line represents a single io action in the following format: 1940 1941 rw, offset, length 1942 1943 where rw=0/1 for read/write, and the offset and length entries being in bytes. 1944 1945 This format is not supported in Fio versions => 1.20-rc3. 1946 1947 1948 8.2 Trace file format v2 1949 ------------------------ 1950 The second version of the trace file format was added in Fio version 1.17. 1951 It allows to access more then one file per trace and has a bigger set of 1952 possible file actions. 1953 1954 The first line of the trace file has to be: 1955 1956 fio version 2 iolog 1957 1958 Following this can be lines in two different formats, which are described below. 1959 1960 The file management format: 1961 1962 filename action 1963 1964 The filename is given as an absolute path. The action can be one of these: 1965 1966 add Add the given filename to the trace 1967 open Open the file with the given filename. The filename has to have 1968 been added with the add action before. 1969 close Close the file with the given filename. The file has to have been 1970 opened before. 1971 1972 1973 The file io action format: 1974 1975 filename action offset length 1976 1977 The filename is given as an absolute path, and has to have been added and opened 1978 before it can be used with this format. The offset and length are given in 1979 bytes. The action can be one of these: 1980 1981 wait Wait for 'offset' microseconds. Everything below 100 is discarded. 1982 read Read 'length' bytes beginning from 'offset' 1983 write Write 'length' bytes beginning from 'offset' 1984 sync fsync() the file 1985 datasync fdatasync() the file 1986 trim trim the given file from the given 'offset' for 'length' bytes 1987 1988 1989 9.0 CPU idleness profiling 1990 -------------------------- 1991 In some cases, we want to understand CPU overhead in a test. For example, 1992 we test patches for the specific goodness of whether they reduce CPU usage. 1993 fio implements a balloon approach to create a thread per CPU that runs at 1994 idle priority, meaning that it only runs when nobody else needs the cpu. 1995 By measuring the amount of work completed by the thread, idleness of each 1996 CPU can be derived accordingly. 1997 1998 An unit work is defined as touching a full page of unsigned characters. Mean 1999 and standard deviation of time to complete an unit work is reported in "unit 2000 work" section. Options can be chosen to report detailed percpu idleness or 2001 overall system idleness by aggregating percpu stats. 2002 2003 2004 10.0 Verification and triggers 2005 ------------------------------ 2006 Fio is usually run in one of two ways, when data verification is done. The 2007 first is a normal write job of some sort with verify enabled. When the 2008 write phase has completed, fio switches to reads and verifies everything 2009 it wrote. The second model is running just the write phase, and then later 2010 on running the same job (but with reads instead of writes) to repeat the 2011 same IO patterns and verify the contents. Both of these methods depend 2012 on the write phase being completed, as fio otherwise has no idea how much 2013 data was written. 2014 2015 With verification triggers, fio supports dumping the current write state 2016 to local files. Then a subsequent read verify workload can load this state 2017 and know exactly where to stop. This is useful for testing cases where 2018 power is cut to a server in a managed fashion, for instance. 2019 2020 A verification trigger consists of two things: 2021 2022 1) Storing the write state of each job 2023 2) Executing a trigger command 2024 2025 The write state is relatively small, on the order of hundreds of bytes 2026 to single kilobytes. It contains information on the number of completions 2027 done, the last X completions, etc. 2028 2029 A trigger is invoked either through creation ('touch') of a specified 2030 file in the system, or through a timeout setting. If fio is run with 2031 --trigger-file=/tmp/trigger-file, then it will continually check for 2032 the existence of /tmp/trigger-file. When it sees this file, it will 2033 fire off the trigger (thus saving state, and executing the trigger 2034 command). 2035 2036 For client/server runs, there's both a local and remote trigger. If 2037 fio is running as a server backend, it will send the job states back 2038 to the client for safe storage, then execute the remote trigger, if 2039 specified. If a local trigger is specified, the server will still send 2040 back the write state, but the client will then execute the trigger. 2041 2042 10.1 Verification trigger example 2043 --------------------------------- 2044 Lets say we want to run a powercut test on the remote machine 'server'. 2045 Our write workload is in write-test.fio. We want to cut power to 'server' 2046 at some point during the run, and we'll run this test from the safety 2047 or our local machine, 'localbox'. On the server, we'll start the fio 2048 backend normally: 2049 2050 server# fio --server 2051 2052 and on the client, we'll fire off the workload: 2053 2054 localbox$ fio --client=server --trigger-file=/tmp/my-trigger --trigger-remote="bash -c \"echo b > /proc/sysrq-triger\"" 2055 2056 We set /tmp/my-trigger as the trigger file, and we tell fio to execute 2057 2058 echo b > /proc/sysrq-trigger 2059 2060 on the server once it has received the trigger and sent us the write 2061 state. This will work, but it's not _really_ cutting power to the server, 2062 it's merely abruptly rebooting it. If we have a remote way of cutting 2063 power to the server through IPMI or similar, we could do that through 2064 a local trigger command instead. Lets assume we have a script that does 2065 IPMI reboot of a given hostname, ipmi-reboot. On localbox, we could 2066 then have run fio with a local trigger instead: 2067 2068 localbox$ fio --client=server --trigger-file=/tmp/my-trigger --trigger="ipmi-reboot server" 2069 2070 For this case, fio would wait for the server to send us the write state, 2071 then execute 'ipmi-reboot server' when that happened. 2072 2073 10.1 Loading verify state 2074 ------------------------- 2075 To load store write state, read verification job file must contain 2076 the verify_state_load option. If that is set, fio will load the previously 2077 stored state. For a local fio run this is done by loading the files directly, 2078 and on a client/server run, the server backend will ask the client to send 2079 the files over and load them from there. 2080
