Ubuntu Manpage: zpool-iostat — display logical I/O statistics for ZFS storage pools

Provided by: zfsutils-linux_2.1.5-1ubuntu6~22.04.5_amd64

NAME

       zpool-iostat — display logical I/O statistics for ZFS storage pools

SYNOPSIS

       zpool    iostat    [[[-c SCRIPT] [-lq]]|-rw]    [-T    u|d]   [-ghHLnpPvy]   [pool…|[pool   vdev…]|vdev…]
             [interval [count]]

DESCRIPTION

Displays logical I/O statistics for the given pools/vdevs. Physical I/O statistics may be observed via
iostat(1). If writes are located nearby, they may be merged into a single larger operation. Additional
I/O may be generated depending on the level of vdev redundancy. To filter output, you may pass in a list
of pools, a pool and list of vdevs in that pool, or a list of any vdevs from any pool. If no items are
specified, statistics for every pool in the system are shown. When given an interval, the statistics are
printed every interval seconds until killed. If -n flag is specified the headers are displayed only
once, otherwise they are displayed periodically. If count is specified, the command exits after count
reports are printed. The first report printed is always the statistics since boot regardless of whether
interval and count are passed. However, this behavior can be suppressed with the -y flag. Also note
that the units of K, M, G… that are printed in the report are in base 1024. To get the raw values, use
the -p flag.

-c [SCRIPT1[,SCRIPT2]…]
Run a script (or scripts) on each vdev and include the output as a new column in the zpool iostat
output. Users can run any script found in their ~/.zpool.d directory or from the system
/etc/zfs/zpool.d directory. Script names containing the slash (/) character are not allowed.
The default search path can be overridden by setting the ZPOOL_SCRIPTS_PATH environment variable.
A privileged user can only run -c if they have the ZPOOL_SCRIPTS_AS_ROOT environment variable
set. If a script requires the use of a privileged command, like smartctl(8), then it's
recommended you allow the user access to it in /etc/sudoers or add the user to the
/etc/sudoers.d/zfs file.

If -c is passed without a script name, it prints a list of all scripts. -c also sets verbose
mode (-v).

Script output should be in the form of "name=value". The column name is set to "name" and the
value is set to "value". Multiple lines can be used to output multiple columns. The first line
of output not in the "name=value" format is displayed without a column title, and no more output
after that is displayed. This can be useful for printing error messages. Blank or NULL values
are printed as a '-' to make output AWKable.

The following environment variables are set before running each script:
VDEV_PATH Full path to the vdev
VDEV_UPATH Underlying path to the vdev (/dev/sd*). For use with device mapper,
multipath, or partitioned vdevs.
VDEV_ENC_SYSFS_PATH The sysfs path to the enclosure for the vdev (if any).

-T u|d Display a time stamp. Specify u for a printed representation of the internal representation of
time. See time(2). Specify d for standard date format. See date(1).

-g Display vdev GUIDs instead of the normal device names. These GUIDs can be used in place of
device names for the zpool detach/offline/remove/replace commands.

-H Scripted mode. Do not display headers, and separate fields by a single tab instead of arbitrary
space.

-L Display real paths for vdevs resolving all symbolic links. This can be used to look up the
current block device name regardless of the /dev/disk/ path used to open it.

-n Print headers only once when passed

-p Display numbers in parsable (exact) values. Time values are in nanoseconds.

-P Display full paths for vdevs instead of only the last component of the path. This can be used in
conjunction with the -L flag.

-r Print request size histograms for the leaf vdev's I/O. This includes histograms of individual
I/O (ind) and aggregate I/O (agg). These stats can be useful for observing how well I/O
aggregation is working. Note that TRIM I/O may exceed 16M, but will be counted as 16M.

-v Verbose statistics Reports usage statistics for individual vdevs within the pool, in addition to
the pool-wide statistics.

-y Normally the first line of output reports the statistics since boot: suppress it.

-w Display latency histograms:
total_wait Total I/O time (queuing + disk I/O time).
disk_wait Disk I/O time (time reading/writing the disk).
syncq_wait Amount of time I/O spent in synchronous priority queues. Does not include
disk time.
asyncq_wait Amount of time I/O spent in asynchronous priority queues. Does not include
disk time.
scrub Amount of time I/O spent in scrub queue. Does not include disk time.

-l Include average latency statistics:
total_wait Average total I/O time (queuing + disk I/O time).
disk_wait Average disk I/O time (time reading/writing the disk).
syncq_wait Average amount of time I/O spent in synchronous priority queues. Does not
include disk time.
asyncq_wait Average amount of time I/O spent in asynchronous priority queues. Does not
include disk time.
scrub Average queuing time in scrub queue. Does not include disk time.
trim Average queuing time in trim queue. Does not include disk time.

-q Include active queue statistics. Each priority queue has both pending (pend) and active (activ)
I/O requests. Pending requests are waiting to be issued to the disk, and active requests have
been issued to disk and are waiting for completion. These stats are broken out by priority
queue:
syncq_read/write Current number of entries in synchronous priority queues.
asyncq_read/write Current number of entries in asynchronous priority queues.
scrubq_read Current number of entries in scrub queue.
trimq_write Current number of entries in trim queue.

All queue statistics are instantaneous measurements of the number of entries in the queues. If
you specify an interval, the measurements will be sampled from the end of the interval.

NAME

SYNOPSIS

DESCRIPTION

SEE ALSO