On Tuesday January 11, brad@xxxxxxxxxxx wrote:
G'day all,
Just started my big raid using mdadm --update resync to ensure the parity blocks are A-OK after a kernel panic, and I have been monitoring my Disk IO with
iostat -k 5
Now this is an average for a 5 second period.
I note I'm seeing about 12,456 Kilobytes/sec from each drive, but a cat /proc mdstat is giving me 6716 Kilobytes/sec. Given I'm doing a read consistency check I would expect an mdstat speed 9/10ths of my bulk per-drive read speed. (This array is sda -> sdj)
Am I missing something really obvious?
avg-cpu: %user %nice %sys %iowait %idle 39.18 0.00 60.82 0.00 0.00
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn hda 0.00 0.00 0.00 0 0 sda 97.76 12465.67 0.00 33408 0 sdb 97.76 12465.67 0.00 33408 0 sdc 97.76 12465.67 0.00 33408 0
So this is a 5 second sample... In 5 seconds, 33408 kB were read. That's 6681.6 kB/sec according to my calculator.
So it looks like iostat is reporting something wrongly. I would look there first.
Ok, fair call on those stats. Having said that, we are talking 6.6 MB/sec per disk. Do I take it the /proc/mdstat figure of 6 MB/sec is not a total array rebuild speed, but a speed per array member?
Regards, Brad - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
