Iostat Results For Multi Path Disks

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Here is a sample of running iostat on a server that has a LUN from a SAN with multiple paths. I am specifying a device list that just grabs the bits related to the multi path device:

$ iostat -dxkt 1 2 sdf sdg sdh sdi dm-7 dm-8 dm-9
Linux 2.6.18-371.8.1.el5 (db21b.den.sans.org) 06/20/2014

Time: 02:30:23 PM
Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await svctm %util sdf 0.66 52.32 3.57 34.54 188.38 347.52 28.13 0.14 3.62 0.87 3.31
sdg 0.66 52.29 3.57 34.56 189.79 347.48 28.18 0.14 3.72 0.87 3.32
sdh 0.00 0.00 0.00 0.00 0.00 0.00 14.19 0.00 2.90 2.90 0.00
sdi 0.00 0.00 0.00 0.00 0.00 0.00 14.19 0.00 2.87 2.87 0.00
dm-7 0.00 0.00 8.46 173.75 378.17 695.00 11.78 3.41 18.68 0.35 6.46
dm-8 0.00 0.00 8.46 173.75 378.17 695.00 11.78 3.41 18.68 0.36 6.47
dm-9 0.00 0.00 8.46 173.75 378.17 695.00 11.78 3.41 18.68 0.36 6.48

Time: 02:30:24 PM
Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await svctm %util sdf 0.00 54.00 7.00 48.00 88.00 408.00 18.04 0.12 2.11 1.20 6.60
sdg 0.00 13.00 1.00 26.00 4.00 156.00 11.85 0.01 0.52 0.48 1.30
sdh 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sdi 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-7 0.00 0.00 8.00 141.00 92.00 564.00 8.81 0.25 1.69 0.53 7.90
dm-8 0.00 0.00 8.00 141.00 92.00 564.00 8.81 0.25 1.70 0.54 8.00
dm-9 0.00 0.00 8.00 141.00 92.00 564.00 8.81 0.25 1.70 0.54 8.00

sdf,sdg,sdh,sdi – four paths for LUN (sdf and sdg are the active paths)
dm-7 – device-mapper pseudo device for the mpath device dm-8 – device-mapper pseudo-device for the partition spanning the entire mpath device dm-9 – device-mapper pseudo-device for the LVM LV created on the mpath device

The first sample from iostat is the historical data so lets ignore it. The second sample are the stats for a 1 second interval.

I see the stats for sdf and sdg are roughly equal but they differ

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