This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


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

To: Nick Couchman <Nick.Couchman@xxxxxxxxx>
Subject: Re: [Xen-users] Xen and I/O Intensive Loads
From: "Fajar A. Nugraha" <fajar@xxxxxxxxx>
Date: Thu, 27 Aug 2009 16:36:04 +0700
Cc: XEN Mailing List <xen-users@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Thu, 27 Aug 2009 02:36:43 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <4A9507E90200009900017BED@xxxxxxxxxxxxxxxxxxxxx>
List-help: <mailto:xen-users-request@lists.xensource.com?subject=help>
List-id: Xen user discussion <xen-users.lists.xensource.com>
List-post: <mailto:xen-users@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=unsubscribe>
References: <4A9507E90200009900017BED@xxxxxxxxxxxxxxxxxxxxx>
Sender: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
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.


Xen-users mailing list