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All rights reserved. 23.\" Copyright (c) 2012 Cyril Plisko. All Rights Reserved. 24.\" Copyright (c) 2017 Datto Inc. 25.\" Copyright (c) 2018 George Melikov. All Rights Reserved. 26.\" Copyright 2017 Nexenta Systems, Inc. 27.\" Copyright (c) 2017 Open-E, Inc. All Rights Reserved. 28.\" 29.Dd March 16, 2022 30.Dt ZPOOL-IOSTAT 8 31.Os 32. 33.Sh NAME 34.Nm zpool-iostat 35.Nd display logical I/O statistics for ZFS storage pools 36.Sh SYNOPSIS 37.Nm zpool 38.Cm iostat 39.Op Oo Oo Fl c Ar SCRIPT Oc Oo Fl lq Oc Oc Ns | Ns Fl rw 40.Op Fl T Sy u Ns | Ns Sy d 41.Op Fl ghHLnpPvy 42.Oo Ar pool Ns … Ns | Ns Oo Ar pool vdev Ns … Oc Ns | Ns Ar vdev Ns … Oc 43.Op Ar interval Op Ar count 44. 45.Sh DESCRIPTION 46Displays logical I/O statistics for the given pools/vdevs. 47Physical I/O statistics may be observed via 48.Xr iostat 1 . 49If writes are located nearby, they may be merged into a single 50larger operation. 51Additional I/O may be generated depending on the level of vdev redundancy. 52To filter output, you may pass in a list of pools, a pool and list of vdevs 53in that pool, or a list of any vdevs from any pool. 54If no items are specified, statistics for every pool in the system are shown. 55When given an 56.Ar interval , 57the statistics are printed every 58.Ar interval 59seconds until killed. 60If 61.Fl n 62flag is specified the headers are displayed only once, otherwise they are 63displayed periodically. 64If 65.Ar count 66is specified, the command exits after 67.Ar count 68reports are printed. 69The first report printed is always the statistics since boot regardless of whether 70.Ar interval 71and 72.Ar count 73are passed. 74However, this behavior can be suppressed with the 75.Fl y 76flag. 77Also note that the units of 78.Sy K , 79.Sy M , 80.Sy G Ns … 81that are printed in the report are in base 1024. 82To get the raw values, use the 83.Fl p 84flag. 85.Bl -tag -width Ds 86.It Fl c Op Ar SCRIPT1 Ns Oo , Ns Ar SCRIPT2 Oc Ns … 87Run a script (or scripts) on each vdev and include the output as a new column 88in the 89.Nm zpool Cm iostat 90output. 91Users can run any script found in their 92.Pa ~/.zpool.d 93directory or from the system 94.Pa /etc/zfs/zpool.d 95directory. 96Script names containing the slash 97.Pq Sy / 98character are not allowed. 99The default search path can be overridden by setting the 100.Sy ZPOOL_SCRIPTS_PATH 101environment variable. 102A privileged user can only run 103.Fl c 104if they have the 105.Sy ZPOOL_SCRIPTS_AS_ROOT 106environment variable set. 107If a script requires the use of a privileged command, like 108.Xr smartctl 8 , 109then it's recommended you allow the user access to it in 110.Pa /etc/sudoers 111or add the user to the 112.Pa /etc/sudoers.d/zfs 113file. 114.Pp 115If 116.Fl c 117is passed without a script name, it prints a list of all scripts. 118.Fl c 119also sets verbose mode 120.No \&( Ns Fl v Ns No \&). 121.Pp 122Script output should be in the form of "name=value". 123The column name is set to "name" and the value is set to "value". 124Multiple lines can be used to output multiple columns. 125The first line of output not in the 126"name=value" format is displayed without a column title, 127and no more output after that is displayed. 128This can be useful for printing error messages. 129Blank or NULL values are printed as a '-' to make output AWKable. 130.Pp 131The following environment variables are set before running each script: 132.Bl -tag -compact -width "VDEV_ENC_SYSFS_PATH" 133.It Sy VDEV_PATH 134Full path to the vdev 135.It Sy VDEV_UPATH 136Underlying path to the vdev 137.Pq Pa /dev/sd* . 138For use with device mapper, multipath, or partitioned vdevs. 139.It Sy VDEV_ENC_SYSFS_PATH 140The sysfs path to the enclosure for the vdev (if any). 141.El 142.It Fl T Sy u Ns | Ns Sy d 143Display a time stamp. 144Specify 145.Sy u 146for a printed representation of the internal representation of time. 147See 148.Xr time 2 . 149Specify 150.Sy d 151for standard date format. 152See 153.Xr date 1 . 154.It Fl g 155Display vdev GUIDs instead of the normal device names. 156These GUIDs can be used in place of device names for the zpool 157detach/offline/remove/replace commands. 158.It Fl H 159Scripted mode. 160Do not display headers, and separate fields by a 161single tab instead of arbitrary space. 162.It Fl L 163Display real paths for vdevs resolving all symbolic links. 164This can be used to look up the current block device name regardless of the 165.Pa /dev/disk/ 166path used to open it. 167.It Fl n 168Print headers only once when passed 169.It Fl p 170Display numbers in parsable (exact) values. 171Time values are in nanoseconds. 172.It Fl P 173Display full paths for vdevs instead of only the last component of the path. 174This can be used in conjunction with the 175.Fl L 176flag. 177.It Fl r 178Print request size histograms for the leaf vdev's I/O. 179This includes histograms of individual I/O (ind) and aggregate I/O (agg). 180These stats can be useful for observing how well I/O aggregation is working. 181Note that TRIM I/O may exceed 16M, but will be counted as 16M. 182.It Fl v 183Verbose statistics Reports usage statistics for individual vdevs within the 184pool, in addition to the pool-wide statistics. 185.It Fl y 186Normally the first line of output reports the statistics since boot: 187suppress it. 188.It Fl w 189Display latency histograms: 190.Bl -tag -compact -width "asyncq_read/write" 191.It Sy total_wait 192Total I/O time (queuing + disk I/O time). 193.It Sy disk_wait 194Disk I/O time (time reading/writing the disk). 195.It Sy syncq_wait 196Amount of time I/O spent in synchronous priority queues. 197Does not include disk time. 198.It Sy asyncq_wait 199Amount of time I/O spent in asynchronous priority queues. 200Does not include disk time. 201.It Sy scrub 202Amount of time I/O spent in scrub queue. 203Does not include disk time. 204.It Sy rebuild 205Amount of time I/O spent in rebuild queue. 206Does not include disk time. 207.El 208.It Fl l 209Include average latency statistics: 210.Bl -tag -compact -width "asyncq_read/write" 211.It Sy total_wait 212Average total I/O time (queuing + disk I/O time). 213.It Sy disk_wait 214Average disk I/O time (time reading/writing the disk). 215.It Sy syncq_wait 216Average amount of time I/O spent in synchronous priority queues. 217Does not include disk time. 218.It Sy asyncq_wait 219Average amount of time I/O spent in asynchronous priority queues. 220Does not include disk time. 221.It Sy scrub 222Average queuing time in scrub queue. 223Does not include disk time. 224.It Sy trim 225Average queuing time in trim queue. 226Does not include disk time. 227.It Sy rebuild 228Average queuing time in rebuild queue. 229Does not include disk time. 230.El 231.It Fl q 232Include active queue statistics. 233Each priority queue has both pending 234.Sy ( pend ) 235and active 236.Sy ( activ ) 237I/O requests. 238Pending requests are waiting to be issued to the disk, 239and active requests have been issued to disk and are waiting for completion. 240These stats are broken out by priority queue: 241.Bl -tag -compact -width "asyncq_read/write" 242.It Sy syncq_read/write 243Current number of entries in synchronous priority 244queues. 245.It Sy asyncq_read/write 246Current number of entries in asynchronous priority queues. 247.It Sy scrubq_read 248Current number of entries in scrub queue. 249.It Sy trimq_write 250Current number of entries in trim queue. 251.It Sy rebuildq_write 252Current number of entries in rebuild queue. 253.El 254.Pp 255All queue statistics are instantaneous measurements of the number of 256entries in the queues. 257If you specify an interval, 258the measurements will be sampled from the end of the interval. 259.El 260. 261.Sh EXAMPLES 262.\" These are, respectively, examples 13, 16 from zpool.8 263.\" Make sure to update them bidirectionally 264.Ss Example 13 : No Adding Cache Devices to a ZFS Pool 265The following command adds two disks for use as cache devices to a ZFS storage 266pool: 267.Dl # Nm zpool Cm add Ar pool Sy cache Pa sdc sdd 268.Pp 269Once added, the cache devices gradually fill with content from main memory. 270Depending on the size of your cache devices, it could take over an hour for 271them to fill. 272Capacity and reads can be monitored using the 273.Cm iostat 274subcommand as follows: 275.Dl # Nm zpool Cm iostat Fl v Ar pool 5 276. 277.Ss Example 16 : No Adding output columns 278Additional columns can be added to the 279.Nm zpool Cm status No and Nm zpool Cm iostat No output with Fl c . 280.Bd -literal -compact -offset Ds 281.No # Nm zpool Cm status Fl c Pa vendor , Ns Pa model , Ns Pa size 282 NAME STATE READ WRITE CKSUM vendor model size 283 tank ONLINE 0 0 0 284 mirror-0 ONLINE 0 0 0 285 U1 ONLINE 0 0 0 SEAGATE ST8000NM0075 7.3T 286 U10 ONLINE 0 0 0 SEAGATE ST8000NM0075 7.3T 287 U11 ONLINE 0 0 0 SEAGATE ST8000NM0075 7.3T 288 U12 ONLINE 0 0 0 SEAGATE ST8000NM0075 7.3T 289 U13 ONLINE 0 0 0 SEAGATE ST8000NM0075 7.3T 290 U14 ONLINE 0 0 0 SEAGATE ST8000NM0075 7.3T 291 292.No # Nm zpool Cm iostat Fl vc Pa size 293 capacity operations bandwidth 294pool alloc free read write read write size 295---------- ----- ----- ----- ----- ----- ----- ---- 296rpool 14.6G 54.9G 4 55 250K 2.69M 297 sda1 14.6G 54.9G 4 55 250K 2.69M 70G 298---------- ----- ----- ----- ----- ----- ----- ---- 299.Ed 300. 301.Sh SEE ALSO 302.Xr iostat 1 , 303.Xr smartctl 8 , 304.Xr zpool-list 8 , 305.Xr zpool-status 8 306