[pve-devel] some news for snapshots

Alexandre DERUMIER aderumier at odiso.com
Mon Aug 27 10:17:54 CEST 2012


>>AFAIK, you can already create a snapshot of COW2 files using 'savevm' command. 
>>So I think the basic code must be there? It is just not implemented inside the 
>>'blockdev-snapshot-sync' command. 

Yes, but savevm pause the vm and make a full snapshot (include memory,etc..), and It can take several minutes if you have big memory vm.

I have read some old mail with patch to do only disk snapshot (flushing pending writes)
http://patchwork.ozlabs.org/patch/64346/
But it's not implemented

I have see new patches to convert savevm hmp command to qmp
http://lists.gnu.org/archive/html/qemu-devel/2012-08/msg02726.html


I'll do some tests with savevm today to see how it's works.


----- Mail original ----- 

De: "Dietmar Maurer" <dietmar at proxmox.com> 
À: "Alexandre DERUMIER" <aderumier at odiso.com>, pve-devel at pve.proxmox.com 
Envoyé: Lundi 27 Août 2012 10:07:02 
Objet: RE: [pve-devel] some news for snapshots 


> for qcow2 internal snapshot: 
> ----------------------------- 
> We can't use qemu-img -c, to create snasphot, when vm is online. (confirmed 
> by Stefan Hajnoczi from qemu mailing) It cause corruptions, and bad things. 
> (I have tested it and had crashed my qcow2 file after some online snapshot 
> and offline rollback) So no online internal snapshot for now. (I have tell the 
> question if online internal snapshot is on the roadmap, don't have response 
> yet from qemu mailing) 

AFAIK, you can already create a snapshot of COW2 files using 'savevm' command. 
So I think the basic code must be there? It is just not implemented inside the 
'blockdev-snapshot-sync' command. 

- Dietmar 




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