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



On Thu, Mar 04, 2010 at 04:55:57PM +0200, Pasi Kärkkäinen wrote:
> 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.
> 

Uhm, that was supposed to say "XCP can do VHD snapshots with LVM storage,
shared across all cluster nodes".

XCP doesn't use LVM snapshots.

-- Pasi

> 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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