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[Xen-users] Xen domU physical partition disk I/O write throughput %50 sl

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Subject: [Xen-users] Xen domU physical partition disk I/O write throughput %50 slower
From: "Hills, Steve" <Steve.Hills@xxxxxxxxxxxx>
Date: Tue, 28 Sep 2010 17:53:15 -0400
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Thread-topic: Xen domU physical partition disk I/O write throughput %50 slower

dom0 is SLES 11 SP1, domU's are paravirtualized SLES 10/11. Local physical disk partition attached to domU via "phy:" (3 SAS disks in RAID1+).

Write throughput is %50 less than compared to write throughput to the same partition from domU. Read throughput is roughly equivalent. Tested via bonnie (e.g. with data size x2 phy mem) and "dd conv=fdatasync" where the partition is empty (no files).  The domU cpu usage is small during the tests.

I've played around with the "Xen best practices", various memory/cpu sizes with dom0/domU, elevator=noop, but there is always a %50 difference.

The question is how do I eliminate/find the bottleneck? I don't see any way to tweak the Xen split drivers/hypervisor in regards to block I/O.

Steve Hills
Teradata Corporation

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