[pve-devel] VM snapshot problem
aderumier at odiso.com
Fri Aug 24 11:53:48 CEST 2012
>>I do not see a big problem - why do you think that does not work
>>for VM snapshot purposes?
because raw file, is just a flat raw ....no metadatas, no copy on write.
Did I miss something ?
I also see that ibm worked last year on a new format: FVD
same performance than raw but with snapshot support
I don't know why it's not already in qemu upstream.
>> xen people claim they can do that without support from san/nas.
For nfs, I really can't see how it's possible. (maybe xen people are crazy :-) Do you have some references mailing list ?)
Vmware use their vaai api, which is integrated in all the big san appliances. But closed source protocol...
Openstack have a netapp (soap) and nexenta (rest) plugin to do this.
>>Yes, but only on one node, and I delete the snapshot afterwards, i.e. we never
>>move such image while snapshots are active!
Ah ok. I really can't help you, I never use lvm in cluster.
----- Mail original -----
De: "Dietmar Maurer" <dietmar at proxmox.com>
À: "Alexandre DERUMIER" <aderumier at odiso.com>
Cc: pve-devel at pve.proxmox.com
Envoyé: Vendredi 24 Août 2012 11:25:40
Objet: RE: VM snapshot problem
> >>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
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
> >> 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!
Alexandre D e rumier
Ingénieur Systèmes et Réseaux
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Fax : 03 20 68 90 88
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