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] How to get rid of IO-Bottleneck?

To: "Martin Fernau" <m.fernau@xxxxxxxxxx>,<xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-users] How to get rid of IO-Bottleneck?
From: "Robert Dunkley" <Robert@xxxxxxxxx>
Date: Fri, 3 Apr 2009 08:36:10 +0100
Delivery-date: Fri, 03 Apr 2009 00:42:14 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
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: <49D5ACF9.70305@xxxxxxxxxxxxxxxxx> <200904030918.38195.m.fernau@xxxxxxxxxx>
Sender: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: Acm0K9w1x/D0Hr78TgiKkUbj5FZkqAAAhhsQ
Thread-topic: [Xen-users] How to get rid of IO-Bottleneck?
I have seen lower performance with fake/software raid (Higher CPU load
and no raid 1 read interleaving) but not enough to be a serious deal
breaker for light use. 

A decent cached raid controller should help in the situation below as it
should reorder writes and reduce disk write thrashing. SSDs would pretty
much eliminate the problem but since the user has 1Tb disks I assume
SSDs will not provide enough storage for the money.


-----Original Message-----
From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Martin
Sent: 03 April 2009 08:19
To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] How to get rid of IO-Bottleneck?

I have the same performance issues on systems using fakeraid.
Systems with a real active raid controller using SAS harddrives haven't
problem. They are running as mooth as a standalone system.
If you too using fakeraid (meaning that you use dodmraid) or software
then I'm afraid that you can't do much here. This is because the raid
consumes some amount of your cpu power to calculate and maintain the


> Hi,
> I'm running a Xen (Debian Lenny / 3.3.1 / / 2x1T SATA RAID1 /
> 8G RAM)-Server with ~8-12 VMs (LVM based - NOOP shedule). Each VM is
> running Postgre, Tomcat, Apache. If we do our daily testings, the
> disk-io-performance  is terrible.
> As far as I understood reads are cached within the VMs, so this should
> not be the problem. I think the high number of writes is killing the
> hdd. Is there a way to do something like "async write", or what else
> could I do to speedup the VMs even if there is a lot of disk-io?
> Thanks,
> Fabian
> _______________________________________________
> Xen-users mailing list
> Xen-users@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-users

Xen-users mailing list

The SAQ Group

Registered Office: 18 Chapel Street, Petersfield, Hampshire GU32 3DZ
SAQ is the trading name of SEMTEC Limited. Registered in England & Wales
Company Number: 06481952

http://www.saqnet.co.uk AS29219

SAQ Group Delivers high quality, honestly priced communication and I.T. 
services to UK Business.

Broadband : Domains : Email : Hosting : CoLo : Servers : Racks : Transit : 
Backups : Managed Networks : Remote Support.

ISPA Member

Find us in http://www.thebestof.co.uk/petersfield

Xen-users mailing list