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[Xen-users] xen & iSCSI

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] xen & iSCSI
From: Daniel De Marco <ddm@xxxxxxxxxxxxxxx>
Date: Thu, 24 Sep 2009 14:13:22 -0400
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Hi,

I'm setting up xen (on centos 5.3) and I'm facing a weird performance
issue with iSCSI.

I attach the iSCSI targets to dom0 and if I use them from dom0 I obtain
good performance with simple dd tests (~100MB/s both reading and
writing).

I then use the block devices for the domU and if I repeat the same dd test
from within the domU the write performace is still good (~100MB/s), but
the read performance is cut in half (~55MB/s).

I tried changing several parameters like read_ahead and such, but I can
not obtain a good read performance in the domU.

Any idea?

Thanks, Daniel.

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