[Libvir] Snapshots in Libvirt

[Daniel P. Berrange]

On Thu, Feb 28, 2008 at 11:44:28AM -0500, Daniel Veillard wrote:
> On Thu, Feb 28, 2008 at 06:33:13PM +0200, Gabriel Kaufmann wrote:
> > 
> >    Hi,
> > 
> > 
> >    Can  anyone  tell  me  on  which  version  of  libvirt,  the  snapshot
> >    functionality is  planned to be implemented fos Xen and KVM?
> > 
> > 
> >    By  snapshot  I  mean  to  be able to save the state of the machine in
> >    order to be able to revert to the snapshot.
> 
> Can you provide pointers to descriptions of Xen and KVM support for this ? 
> My take was that the main problem was with snapshotting support at the
> filesystem level, and I think only LVM has support for this,

It needs closely co-ordination between the HV & the filesystem and is not
possible to implement in the general case.  QEMU/KVM supports snapshots
only if your disks are in QCow2 format. There's no way to co-ordinate its
snapshots with LVM snapshotting.

And if you're using raw partitions, iSCSI, FiberChannel, you're totally
out of luck

This is not to say we shouldn't impleemnt snapshots in the API for libvirt.
Just that there will be *very* limited scenarios in which it will be usable

Dan.
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