Re: [Xen-users] xen storage options - plase advise

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Thu, Mar 04, 2010 at 09:28:58AM -0500, John Madden wrote:
>> i suggest you to use LVM and NOT CLVM. CLVM does not support
>> snapshotting at all.
>
> CLVM itself doesn't allow snapshotting, but you can still run snapshots  
> from within your domU's.
>
> But keep in mind that running a snapshot from dom0 with a LV that is  
> phy: exported to your domU won't provide a consistent snapshot anyway,  
> so I don't see the point in snapshotting from dom0.  (domU maintains its  
> own buffer cache, has no idea that a snapshot has been created from  
> dom0; dom0 has no idea what domU is doing, can only see the blocks that  
> have been committed to disk, which is not necessarily consistent.  This  
> is roughly equivalent to creating a snapshot on your SAN without first  
> syncing the client.)
>
> Use CLVM.  If you need snapshots, do them within the domU.
>

Or use XCP. It can do LVM snapshots in a cluster, with shared storage.

XCP doesn't use CLVM, but it uses other methods to share the LVM volumes
across all hosts/nodes in the cluster.

-- Pasi


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