[DRBD-user] Slow write performance

listslut listslut at outofoptions.net
Thu Jun 30 17:19:21 CEST 2011


I didn't set this cluster up but that information was documented by the 
previous admin here:

http://crunchtools.com/kvm-cluster-with-drbd-gfs2/

It is now to the point where provisioning space for a new VM is a day 
long process with a load level that brings down the server.  I did these 
tests this morning.  If the formatting gets really bad on send the non 
drbd portion of the raid shows 2.14.79 MB writes and the drbd portion of 
the raid shows 4.65MB to start and drops off to around 1.5MB average.


Iostat test on the non drbd portion of the raid.

Device:             tps    MB_read/s    MB_wrtn/s    MB_read    MB_wrtn
cciss/c0d0         622.61         0.03       214.79          0        427
drbd0                 329.65         0.03         1.26             
0          2

Iostat test on the drbd portion of the raid.

Device:            tps    MB_read/s    MB_wrtn/s    MB_read    MB_wrtn
cciss/c0d0       52.26         0.02         4.65          0          9
drbd0           1182.41         0.02         4.65          0          9

Device:            tps    MB_read/s    MB_wrtn/s    MB_read    MB_wrtn
cciss/c0d0      134.83         0.01         2.15          0          4
drbd0              449.75         0.01         1.75          0          3

Device:            tps    MB_read/s    MB_wrtn/s    MB_read    MB_wrtn
cciss/c0d0      105.00         0.00         1.60          0          3
    drbd0           407.00         0.00         1.59          0          3

Device:            tps    MB_read/s    MB_wrtn/s    MB_read    MB_wrtn
cciss/c0d0       90.95         0.00         1.54          0          3
   drbd0           394.97         0.00         1.54          0          3

Device:            tps    MB_read/s    MB_wrtn/s    MB_read    MB_wrtn
cciss/c0d0      114.93         0.00         1.68          0          3
    drbd0           430.35         0.00         1.68          0          3

Clustering was broken after an upgrade before I got here.  I upgraded 
both systems to the latest RHEL 5 about a month ago.    The drbd was 
compiled locally and is version drbd-8.2.6.

Thank You
Ken




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