I''m seeing slower then expected disk IO. Also, using sar, it seems the
disk is measuring different utilization on the domU then the dom0.
I''ve
attached to the disk with:
"phy:/dev/PowerVault00/KojiShare,xvdb1,w"
That logical volume has a physical volume of an attached 15 disk raid6
array (an MD1000 from dell).
Here is the sar data I''m referencing:
http://mmcgrath.fedorapeople.org/dom0
and
http://mmcgrath.fedorapeople.org/domU
The disk does have one other guest attached to it but that guest has very
little disk IO.
Other items of note: the data periods above happened during a bacula
backup. I would have expected much higher data throughput. We''re
talking
about an average read speed of 3.58 MBytes/s and it says its 95% utilized.
Meanwhile the dom0 says its only 51% utilized.
Additionally on both the domU and dom0 we''re not seeing much iowait.
On
the domU we''re only talking about an average of 14%. If the disks
truly
were fully utilized, I''d expect that to be much higher. These are both
RHEL5 boxes. dom0=2.6.18-92.1.18.el5xen. domU=2.6.18-105.el5xen. Also
both are x86_64.
Thoughts?
-Mike
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