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Re: SW RAID read performance



Hm ah nice.

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.00    0.00    5.05   94.95    0.00    0.00

Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await svctm %util sda 277.78 0.00 100.00 1.01 23660.61 4.04 468.56 0.68 6.73 6.49 65.56 sdb 97.98 0.00 104.04 3.03 12836.36 12.12 240.00 1.25 16.51 3.29 35.25 md0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 md2 0.00 0.00 578.79 0.00 36496.97 0.00 126.12 0.00 0.00 0.00 0.00 md3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 md1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.99    0.00    5.94   93.07    0.00    0.00

Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await svctm %util sda 205.94 0.00 74.26 0.99 17841.58 3.96 474.32 0.47 6.34 6.30 47.43 sdb 213.86 0.00 76.24 0.00 18186.14 0.00 477.09 0.52 6.57 6.55 49.90


Both a+b are both reading simultaneously.


On Thu, 3 Aug 2006, Dave Ewart wrote:

On Thursday, 03.08.2006 at 15:30 -0400, Justin Piszcz wrote:

I've only ran the benchmarks on a single controller.  Run a test for me,
read a lot of data on the drive and show us iostat -x -k 1 and see if it
reads from both drives at the same time.

http://www.sungate.co.uk/tmp/iostat.log - iostat log while cat-ing a
large file on /dev/md2

$ cat /proc/mdstat
Personalities : [raid1]
md1 : active raid1 sdb2[0] sda2[1]
     19534976 blocks [2/2] [UU]

md3 : active raid1 sdb3[1] sda3[0]
     4000064 blocks [2/2] [UU]

md2 : active raid1 sdb4[0] sda4[1]
     156071360 blocks [2/2] [UU]

md0 : active raid1 sdb1[0] sda1[1]
     19534912 blocks [2/2] [UU]

unused devices: <none>

Not entirely sure how to interpret the results, but there is some
suggestion that it is reading from both disks...

Dave.
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