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[Xen-users] Re: [linux-lvm] LVM Read/Write speed <10% drive's normal spe

To: Stephen.Hamer@xxxxxxxxxx, LVM general discussion and development <linux-lvm@xxxxxxxxxx>
Subject: [Xen-users] Re: [linux-lvm] LVM Read/Write speed <10% drive's normal speed
From: "Bryn M. Reeves" <bmr@xxxxxxxxxx>
Date: Thu, 17 Sep 2009 11:21:42 +0100
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On Wed, 2009-09-16 at 21:49 +0000, Stephen Hamer wrote:
> Hello all,
> I've been searching through the archives and the internet for a while
> now, and can't seem to find anything that helps me out. I hope you
> don't my posting this to both xen-users and linux-lvm simultaneously,
> but i figured it'd help keep the solution in one place... even though
> it'll be the same across two places... Anyways:
> My setup is this:
>         Xen 3.3 hypervisor (from the ubuntu repositories)
>         Ubuntu 9.04 server
>         Kernel and module listed here:
> http://www.infohit.net/blog/post/running-xen-on-ubuntu-intrepid-and-jaunty.html
> The dom0 and domUs in my Xen setup are all Ubuntu 9.04, using that
> kernel. (I'm not sure if the kernel has something to do with it, so i
> included it just in case.) All the domUs are set up to use LVM. The
> dom0 uses a straight ext3 fs on /dev/sda1. The domUs use ext3 fs's
> within LVMs (using LVM2) set up on /dev/sda5.

What is the configuration of the guest's storage? I.e. what type of virt
driver are you using to expose the dom0 storage to the domUs? This can
have a massive impact on the performance levels you can achieve.

You should also test the performance of these underlying devices in the
domUs - i.e. benchmark read (and if possible write) performance of
the /dev/sd*, /dev/hd* or /dev/xvd* devices seen in domU (or whatever
other type of virtual disks you are using).


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