On Sep 27, 2010, at 9:54 PM, Ross Walker rswwalker@gmail.com wrote:
On Sep 27, 2010, at 8:16 PM, Tom Bishop bishoptf@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.
I was wrong about the sector size, it's regular 512 byte sectors.
It still makes sense to look at the partition offset, but I would also look at the cabling too.
-Ross