Better iostat visibility of ZFS vdevs
All ZFS users are familiar with ‘zpool iostat’ command, however, it is not easily translated into Linux ‘iostat’ command. Using large pools with many disks will result in a mess, where it’s hard to identify which disk is which, and going to a translation table from time to time, to identify a suspect slow disk.
Linux ‘iostat’ command allows to use aliases, and if you’r using vdev_id.conf file, and you are using ZFS aliased names, you can harness the same naming to your ‘iostat’ command. See my command example below – note that in this setup I do not use multipath or other DM devices, but a direct approach to /dev/sd devices. Also – in this case – I have a few (slightly more than a dozen) disks, so no need to address /dev/sd[a-z][a-z] devices:
iostat -kt 5 -j vdev -x /dev/sd? /dev/nvme0n1You can chain more devices to the end of this line. The result should be something like this:
07/04/2021 10:36:54 AM
avg-cpu: %user %nice %system %iowait %steal %idle
0.26 0.00 0.87 1.49 0.00 97.39
r/s w/s rkB/s wkB/s rrqm/s wrqm/s %rrqm %wrqm r_await w_await aqu-sz rareq-sz wareq-sz svctm %util Device
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 nvme0n1
42.80 15.40 5461.60 1938.40 0.00 0.00 0.00 0.00 0.50 0.87 0.01 127.61 125.87 1.12 6.50 sata500g2
52.20 0.00 6631.20 0.00 0.00 0.00 0.00 0.00 0.43 0.00 0.00 127.03 0.00 1.40 7.30 sata500g1
40.60 0.40 5196.80 51.20 0.00 0.00 0.00 0.00 0.44 0.50 0.00 128.00 128.00 1.41 5.80 sata500g4
71.60 6.20 9148.00 776.80 0.00 0.00 0.00 0.00 0.45 0.48 0.00 127.77 125.29 1.34 10.46 sata500g3
35.00 6.00 4463.20 768.00 0.00 0.00 0.00 0.00 0.44 0.53 0.00 127.52 128.00 1.24 5.08 sata1t
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 mid1
28.80 10.60 748.00 84.00 0.00 0.00 0.00 0.00 1.55 0.53 0.04 25.97 7.92 1.11 4.36 top4
5.00 18.00 122.40 106.40 0.00 0.00 0.00 0.00 13.32 18.32 0.39 24.48 5.91 1.18 2.72 top5
4.60 27.40 124.00 160.80 0.00 0.00 0.00 0.00 10.35 15.71 0.46 26.96 5.87 1.09 3.48 top2
26.40 12.20 676.80 88.80 0.00 0.00 0.00 0.00 2.14 0.52 0.05 25.64 7.28 1.07 4.12 bot3
4.60 25.40 104.80 137.60 0.00 0.00 0.00 0.00 5.26 0.64 0.04 22.78 5.42 0.31 0.94 mid4
5.40 19.00 130.40 119.20 0.00 0.00 0.00 0.00 3.81 0.52 0.02 24.15 6.27 0.57 1.38 mid5
25.00 12.00 596.80 80.00 0.00 0.20 0.00 1.64 3.61 0.13 0.08 23.87 6.67 1.03 3.80 mid2
28.00 11.20 678.40 81.60 0.00 0.00 0.00 0.00 3.67 0.59 0.10 24.23 7.29 1.23 4.84 bot2
5.00 23.40 114.40 140.80 0.00 0.00 0.00 0.00 9.28 0.43 0.05 22.88 6.02 0.51 1.44 bot4
5.00 27.00 120.80 151.20 0.00 0.00 0.00 0.00 4.04 0.75 0.03 24.16 5.60 0.49 1.56 bot5
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 mid3
27.40 8.60 661.60 77.60 0.00 0.00 0.00 0.00 1.77 0.49 0.04 24.15 9.02 1.16 4.18 bot1
27.00 9.60 692.00 84.80 0.00 0.00 0.00 0.00 2.10 0.52 0.05 25.63 8.83 1.15 4.20 top1
