[pve-devel] VM snapshot problem

Dietmar Maurer dietmar at proxmox.com
Fri Aug 24 11:25:40 CEST 2012

> >>The problem with that is that most users use LVM, NFS or RAW files on
> local storage.
> >>So how can we snapshot such images?
> >>
> >>For NFS and RAW files we can create and external snapshot (base image +
> writable image file)?
> I don't think it's possible. this is main reason why qcow2 exist.

I do not see a big problem - why do you think that does not work
for VM snapshot purposes?

> for nfs,it's possible if you have a san/nas which support snapshot on his
> filesytem. Like netapp nfs for exemple. (but need to implement snapshot api)

xen people claim they can do that without support from san/nas.

> For local raw file, it should be possible with zfs or btrfs.  (remote linux nfs
> storage with zfs,btrfs should work too, implement snasphots via ssh
> commands)

sorry, but we can't use any of those file systems for known reasons.

> (but you can convert raw to qcow2 also)

I am looking for a solution - not a workaround ;-)

> I known that qemu developper are currently working for optimize qcow2
> performance.
> >> But how can we handle LVM (lvm snapshots on shared storage does not
> work at all)?
> I really don't know.
> for "new" lvm format (dm-thinp) , it doesn't work.
> For "old" lvm format, maybe. (But I have read some articles with bad
> performance about it)
> Don't you use already lvm snapshot for backups ?

Yes, but only on one node, and I delete the snapshot afterwards, i.e. we never
move such image while snapshots are active!

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