Listing Virtual Device I/O Statistics
The zpool iostat -v command can display I/O statistics for virtual devices. Use this command to identify abnormally slow devices or to observe the distribution of I/O generated by ZFS. See the following three examples. The last two examples display a multigroup configuration.
$ zpool iostat -v tank
capacity operations bandwidth
pool alloc free read write read write
----------------------- ----- ----- ----- ----- ----- -----
tank 2.69G 1.81T 0 29 252 14.2M
c0t5000C5001032271Bd0 1.34G 927G 0 14 130 7.09M
c0t5000C50010349387d0 1.34G 927G 0 14 122 7.09M
----------------------- ----- ----- ----- ----- ----- -----$ zpool iostat -v tank
capacity operations bandwidth
pool alloc free read write read write
------------------------- ----- ----- ----- ----- ----- -----
tank 810M 1.81T 0 390 536 32.1M
mirror-0 405M 928G 0 194 232 16.1M
c0t5000C5001032271Bd0 - - 0 37 1.07K 16.2M
c0t5000C50010349387d0 - - 0 38 858 16.1M
mirror-1 405M 928G 0 195 304 16.1M
c0t5000C5001033963Fd0 - - 0 37 1.14K 16.2M
c0t5000C5001033024Fd0 - - 0 38 858 16.2M
------------------------- ----- ----- ----- ----- ----- -----$ zpool iostat -v tank
capacity operations bandwidth
pool alloc free read write read write
------------------------- ----- ----- ----- ----- ----- -----
tank 258M 5.44T 0 321 876 31.5M
raidz1-0 128M 2.72T 0 160 29 15.9M
c0t5000C5001032271Bd0 - - 0 33 1.40K 8.07M
c0t5000C50010349387d0 - - 0 30 1.37K 8.07M
c0t5000C5001033963Fd0 - - 0 30 1.37K 8.07M
raidz1-1 130M 2.72T 0 160 847 15.5M
c0t5000C5001033024Fd0 - - 1 34 2.20K 8.10M
c0t5000C500103C9817d0 - - 0 34 1.37K 7.87M
c0t5000C50010324F67d0 - - 0 34 1.37K 8.10M
------------------------- ----- ----- ----- ----- ----- -----The zpool iostat -v command provides specific information for each level of the pool configuration:
-
Pool level shows the sum of the group level data.
-
Group level shows the compiled data of the mirror or raidz configuration.
-
Leaf level shows information for each physical disk.
Note two important points when viewing I/O statistics for virtual devices:
-
Statistics on disk space use are available only for top-level virtual devices. The way in which disk space is allocated among mirror and RAID-Z virtual devices is particular to the implementation and not easily expressed as a single number.
-
The numbers might not add up exactly as you would expect. In particular, operations across RAID-Z and mirrored devices will not be exactly equal. This difference is particularly noticeable immediately after a pool is created because a significant amount of I/O is done directly to the disks as part of pool creation, which is not accounted for at the mirror level. Over time, these numbers gradually equalize. However, broken, unresponsive, or offline devices can affect this symmetry as well.
You can use interval and count when examining virtual device statistics.
You can also display physical location information about the pool's virtual devices. The following example shows sample output that has been truncated:
$ zpool iostat -lv
capacity operations bandwidth
pool alloc free read write read write
---------- ----- ----- ----- ----- ----- -----
export 2.39T 2.14T 13 27 42.7K 300K
mirror 490G 438G 2 5 8.53K 60.3K
/dev/chassis/lab10rack15/SCSI_Device__2/disk - - 1 0 4.47K 60.3K
/dev/chassis/lab10rack15/SCSI_Device__3/disk - - 1 0 4.45K 60.3K
mirror 490G 438G 2 5 8.62K 59.9K
/dev/chassis/lab10rack15/SCSI_Device__4/disk - - 1 0 4.52K 59.9K
/dev/chassis/lab10rack15/SCSI_Device__5/disk - - 1 0 4.48K 59.9K