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we use iostat -x and check for the await column - per device it shows the total time spent waiting plus the actual handling of the request by the disk
iostat -yzx 5
Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
sdm 0.00 0.00 0.00 1.60 0.00 4.20 5.25 0.00 0.75 0.00 0.75 0.62 0.10
sda 0.00 0.40 0.00 3.00 0.00 24.70 16.47 0.11 37.60 0.00 37.60 7.13 2.14
sdc 0.00 0.00 0.00 0.80 0.00 6.10 15.25 0.01 12.75 0.00 12.75 12.75 1.02
sdb 0.00 0.00 0.00 0.40 0.00 2.40 12.00 0.01 19.50 0.00 19.50 19.50 0.78
sdd 0.00 0.00 0.00 0.80 0.00 6.60 16.50 0.01 10.75 0.00 10.75 10.75 0.86
sdg 0.00 0.00 0.00 1.00 0.00 8.90 17.80 0.02 15.80 0.00 15.80 15.80 1.58
sdf 0.00 0.20 0.00 1.00 0.00 8.00 16.00 0.01 12.80 0.00 82.80 12.80 1.28
sde 0.00 0.00 0.00 0.80 0.00 7.50 18.75 0.01 11.25 0.00 11.25 11.25 0.90
sdk 0.00 0.00 0.00 0.80 0.00 6.50 16.25 0.01 14.25 0.00 14.25 14.25 1.14
sdi 0.00 0.00 0.00 1.00 0.00 7.20 14.40 0.01 11.60 0.00 11.60 11.60 1.16
sdj 0.00 0.00 0.00 0.80 0.00 5.90 14.75 0.01 13.50 0.00 13.50 13.50 1.08
sdh 0.00 0.00 0.00 0.80 0.00 5.60 14.00 0.01 13.25 0.00 13.25 13.25 1.06
sdl 0.00 0.00 0.00 1.00 0.00 7.20 14.40 0.01 14.20 0.00 14.20 14.20 1.42
sdn 0.00 0.00 0.00 1.60 0.00 4.20 5.25 0.00 0.88 0.00 0.88 0.75 0.12
md1 0.00 0.00 0.00 0.40 0.00 3.20 16.00
sdq 0.00 0.00 0.00 0.60 0.00 5.20 17.33 0.01 12.67 0.00 82.67 12.67 0.76
sdr 0.00 0.00 0.00 0.60 0.00 4.20 14.00 0.01 10.00 0.00 10.00 10.00 0.60
we can see from the output that await on some disk is high
my question - what we can do about this ?
any option to resolve this ?