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I'm experiencing unusual load issue on one of our VM which is on SAN storage. As a general practice I ran iostat on the server got very strange numbers.

 avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.00    0.00    0.17   49.75    0.00   50.08

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await  svctm  %util
sda               0.00     0.00    0.00    0.00     0.00     0.00     0.00     3.00    0.00   0.00 100.03
dm-0              0.00     0.00    0.00    0.00     0.00     0.00     0.00     3.00    0.00   0.00 100.00
dm-1              0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00

even if rkB/s & wkB/s both at 0 it still shows %util at 100%.

Let me know if I am misunderstanding the output.

Thanks, Meghanand.

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  • Do you have external disks ? ISCSI, NAS ? They are not stats, by takes iowait. – Dom Jul 26 '13 at 8:55
  • Well I'm unsure about it since the server is hosted with our provider, the only available information is its using SAN storage. – vasco.debian Jul 26 '13 at 9:02
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Well after further investigation with our service provider we found the issue was with the shared SAN storage which was running short of iops, after migrating VM to another SAN issue was resolved.

Thanks, Meghanand

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