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Re: [Xen-users] How to get rid of IO-Bottleneck?

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Subject: Re: [Xen-users] How to get rid of IO-Bottleneck?
From: Martin Fernau <m.fernau@xxxxxxxxxx>
Date: Fri, 3 Apr 2009 09:18:37 +0200
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I have the same performance issues on systems using fakeraid.
Systems with a real active raid controller using SAS harddrives haven't this 
problem. They are running as mooth as a standalone system.
If you too using fakeraid (meaning that you use dodmraid) or software raid 
then I'm afraid that you can't do much here. This is because the raid system 
consumes some amount of your cpu power to calculate and maintain the raid 


> 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
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