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Re: [Xen-users] Xen VMs on GFS volumes

On Friday 09 December 2005 10:09, Anders Bruun Olsen wrote:
> On Fri, Dec 09, 2005 at 10:07:38AM +0100, Anders Bruun Olsen wrote:
> > Again, my setup is with an iscsi storage box (an IBM DS300) which both
> > machines has access to. If I don't run a clustering filesystem and mount
> > the same device on both machines, I run into trouble (obviously). But I
> > am not sure if a partition containing a VM actually needs to be mounted
> > two places at the same time, or if it just really quickly unmounts on
> > the first dom0 and mounts it on the second?
> Forgot to mention that I am using Xen 3.0.0.


theoretically, GFS would work in the case that you have a clustered 
filesystem ,accessible from your two dom0s, and you store the file-backed 
VBDs of your domUs on it, so you don't need cluster-awareness within your 
Unfortunately, GFS doesn't support, AFAIK, r/w mount of files on GFS over the 
loopback-device, which Xen uses to make the VBDs accessible for the domUs.
If you tried to start a domU with that setup, you would get lots of i/o errors 
within your domUs. There's a thread on this list about that and I made the 
same experience.
Maybe OCFS2 would do a better job at this point.

Using partitions of your iscsi box as VBDs for domUs should work fine 
considering live migrations. You don't have to use a cluster filesystem, just 
use e.g. ext3 on a LV of your iscsi-box, put the domU root fs on it, make 
sure you have access to it from both your dom0s, be sure to not have mounted 
it from somewhere and start your domUs.

I have a setup running with Xen 3.0 (testing, release of Monday which you can 
get from the website), the VBDs stored on LVs over fibre channel in my san, 
and migration works nice. For testing purposes I just run a test, domU is 
busy with i/o tests etc., and was migrated approx 400 times in the last 20 
hours - still running :)


Michael Mey                                  
Thinking Objects Software GmbH    |   mailto: michael.mey@xxxxxx 
Lilienthalstrasse 2/1                         |   phone: +49 711 88770-147
70825 Stuttgart-Korntal, Germany  |   fax: +49 711 88770-449

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