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Re: [Xen-users] Xen and I/O Intensive Loads

On Wed, Aug 26, 2009 at 11:01 PM, Nick Couchman<Nick.Couchman@xxxxxxxxx> wrote:
> Hi, folks,
> I'm attempting to run an e-mail server on Xen.  The e-mail system is Novell
> GroupWise, and it serves about 250 users.  The disk volume for the e-mail is
> on my SAN, and I've attached the FC LUN to my Xen host, then used the
> "phy:/dev..." method to forward the disk through to the domU.  I'm running
> into an issue with high I/O wait on the box (~250%) and large load averages
> (20-40 for the 1/5/15 minute average).

Just to be clear : can a native system handle your load?
Try iostat on both dom0 and domU. My guess is that you're I/O bound,
and even moving to it a native physical server won't help, since the
bottleneck is in the disk.

> I was wondering if anyone has ideas
> on tuning the domU to handle this - is there a better way to forward the
> disk device through, should I try using an iSCSI software initiator in the
> domU,

Some past threads on this list suggest otherwise. iSCSI in domU
provides worse performance compared to (for example) iscsi in dom0 and
passing the disk using phy:/.

> or is it just a bad idea to put an I/O load like this in a domU?

If it works on native system it should work on a domU.


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