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Re: [Xen-users] High IOWAIT

To: <xen-users@xxxxxxxxxxxxxxxxxxx>, "Lorenzo Milesi" <lorenzo.milesi@xxxxxxxxxx>
Subject: Re: [Xen-users] High IOWAIT
From: "Nick Couchman" <Nick.Couchman@xxxxxxxxx>
Date: Fri, 06 Jun 2008 06:04:02 -0600
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How is this disk connected to the VM?  XEN's backend methods of connecting disks through dom0 aren't great for high I/O use - one of the classic caveats to virtualization in general is that you don't run your database server or your e-mail server in a VM.  While this may not be true per se, it still indicates that things like e-mail servers have out-of-the-ordinary requirements for disk I/O.  If you're using the "file:" method for this disk in the domU, I suggest trying "tap:aio:" instead.  Also, you may want to try using an iSCSI target/initiator setup (even if the initiator is done in software) to see if that helps.
 
-Nick

>>> On 2008/06/06 at 05:06, Lorenzo Milesi <lorenzo.milesi@xxxxxxxxxx> wrote:
Hi

I've a setup with opensource xen3.0.3 on debian etch.
lately i'm experiencing problems with the main debian domu, which runs
samba cyrus apache and few other services.
i'm having very high machine load due to iowait at 100%. i suppose the
culprit to be cyrus, but i'm not sure. i have 4.5g mail, split in
something like 100000 files. I already remounted my partition with
noatime,nodiratime as suggested by the cyrus site, but didn't help. The
vm has only 1 virtual disk of 100gb, 70% free, on lvm.
is there anything xen could be involved in?

thanks
maxxer
--
Lorenzo Milesi - lorenzo.milesi@xxxxxxxxxx

YetOpen S.r.l. - http://www.yetopen.it/
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