[CentOS] RAID rebuild time and disk utilization....

Ross Walker rswwalker at gmail.com
Mon Sep 27 21:54:27 EDT 2010


On Sep 27, 2010, at 8:16 PM, Tom Bishop <bishoptf at gmail.com> wrote:

> Here are the iostats:
> 
> 
> Device:         rrqm/s   wrqm/s   r/s   w/s   rsec/s   wsec/s avgrq-sz avgqu-sz   await  svctm  %util
> sda               0.15     2.47  0.41  0.82    13.01    26.36    31.97     0.01    6.98   1.01   0.12
> sda1              0.02     0.00  0.00  0.00     0.04     0.00    24.50     0.00    5.38   4.82   0.00
> sda2              0.01     0.00  0.00  0.00     0.03     0.00    37.79     0.00    6.77   5.85   0.00
> sda3              0.12     2.47  0.40  0.82    12.93    26.36    31.98     0.01    6.96   1.01   0.12
> sdb               1.48     0.00 315.21  0.01 40533.39     0.75   128.59    26.94   85.45   2.80  88.24
> sdb1              1.47     0.00 315.21  0.01 40533.30     0.75   128.59    26.94   85.45   2.80  88.24

Average queue size of 26.94 requests, average wait time of 85.45ms, service time of 2.8ms ain't bad, but means the sequential IO is randomizing and backing up the IO.

Chances are this is probably a 4k sector drive and the partition's alignment crosses a 4k page causing double reads. Better to start partitions on sector 2048 instead of 63.

Am I correct on these?

If so I'd break the RAID re-partition and resilver it.

-Ross



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