|ZPOOL-IOSTAT(8)||System Manager's Manual||ZPOOL-IOSTAT(8)|
display logical I/O statistics for ZFS storage
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
flag. Also note that the units of
are printed in the report are in base 1024. To get the raw values, use the
- Run a script (or scripts) on each vdev and include the output as a new
column in the
iostatoutput. 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
-cif 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.
-cis passed without a script name, it prints a list of all scripts.
-calso sets verbose mode (
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:
- 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).
- 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.
- Scripted mode. Do not display headers, and separate fields by a single tab instead of arbitrary space.
- 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.
- Print headers only once when passed
- Display numbers in parsable (exact) values. Time values are in nanoseconds.
- Display full paths for vdevs instead of only the last component of the
path. This can be used in conjunction with the
- 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.
- Verbose statistics Reports usage statistics for individual vdevs within the pool, in addition to the pool-wide statistics.
- Normally the first line of output reports the statistics since boot: suppress it.
- Display latency histograms:
- Total I/O time (queuing + disk I/O time).
- Disk I/O time (time reading/writing the disk).
- Amount of time I/O spent in synchronous priority queues. Does not include disk time.
- Amount of time I/O spent in asynchronous priority queues. Does not include disk time.
- Amount of time I/O spent in scrub queue. Does not include disk time.
- Amount of time I/O spent in rebuild queue. Does not include disk time.
- Include average latency statistics:
- Average total I/O time (queuing + disk I/O time).
- Average disk I/O time (time reading/writing the disk).
- Average amount of time I/O spent in synchronous priority queues. Does not include disk time.
- Average amount of time I/O spent in asynchronous priority queues. Does not include disk time.
- Average queuing time in scrub queue. Does not include disk time.
- Average queuing time in trim queue. Does not include disk time.
- Average queuing time in rebuild queue. Does not include disk time.
- Include active queue statistics. Each priority queue has both pending
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:
- Current number of entries in synchronous priority queues.
- Current number of entries in asynchronous priority queues.
- Current number of entries in scrub queue.
- Current number of entries in trim queue.
- Current number of entries in rebuild 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.
The following command adds two disks for use as cache devices to a ZFS storage pool:
addpool cache sdc sdd
Once added, the cache devices gradually fill with content from
main memory. Depending on the size of your cache devices, it could take over
an hour for them to fill. Capacity and reads can be monitored using the
iostat subcommand as follows:
Additional columns can be added to the
iostat output with
-cvendor,model,size NAME STATE READ WRITE CKSUM vendor model size tank ONLINE 0 0 0 mirror-0 ONLINE 0 0 0 U1 ONLINE 0 0 0 SEAGATE ST8000NM0075 7.3T U10 ONLINE 0 0 0 SEAGATE ST8000NM0075 7.3T U11 ONLINE 0 0 0 SEAGATE ST8000NM0075 7.3T U12 ONLINE 0 0 0 SEAGATE ST8000NM0075 7.3T U13 ONLINE 0 0 0 SEAGATE ST8000NM0075 7.3T U14 ONLINE 0 0 0 SEAGATE ST8000NM0075 7.3T #
-vcsize capacity operations bandwidth pool alloc free read write read write size ---------- ----- ----- ----- ----- ----- ----- ---- rpool 14.6G 54.9G 4 55 250K 2.69M sda1 14.6G 54.9G 4 55 250K 2.69M 70G ---------- ----- ----- ----- ----- ----- ----- ----
|March 16, 2022||Debian|