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Re: [Xen-users] Xen and SAN : snapshot XOR live-migration ?

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Xen and SAN : snapshot XOR live-migration ?
From: Siim Vahtre <siim_@xxxxxxxx>
Date: Fri, 23 Mar 2007 07:29:04 +0200 (EET)
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On Thu, 22 Mar 2007, Franck ELIE wrote:

Please tell me if I am wrong :

Xen needs LVM to perform domU snapshots and snapshots must be performed by dom0.

I'm confused. Why Xen would need LVM to perform any snapshots at all?

By the way, a LVM volume group should not be used by more that one kernel at the same time. So if we use a SAN storage, one volume group should be activated on only one server and deactivated on the others.

AFAIK you can use the LVM volume group in all nodes, but you may not change anything. If you need changes (e.g volume size), you must deactivate the vg in all but one node where you actually do the change, which in your case probably means shutting down all domU's.

Check CLVM, it is cluster-aware.

But if we do that, it should not be possible to perform live migration of domU. My conclusion would be that we have to choose between snapshot or live-migration, but with xen 3.0.3 we can not use both.

I'm pretty sure you can achieve both, it just depends how you set up your storage.

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