[pve-devel] VM snapshot problem

[Alexandre DERUMIER]

see kvm slides from redhat
https://events.linuxfoundation.org/slides/2011/linuxcon-japan/lcj2011_sorensen.pdf

page7
(qed format seem to support snapshot too, I have read that performance is better than qcow2)

"
Snapshots in the I/O stack

The snapshot operation can be performed at multiple
levels of the I/O stack:


QEMU snapshots
--------------
QCOW2, QED

LVM
----

File system snapshots
----------------------
btrfs

Enterprise storage snapshots
----------------------------
NFS, NetApp, EMC etc.

Note: All examples are for storage attached to the host
"

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

De: "Alexandre DERUMIER" <aderumier at odiso.com> 
À: "Dietmar Maurer" <dietmar at proxmox.com> 
Cc: pve-devel at pve.proxmox.com 
Envoyé: Vendredi 24 Août 2012 11:16:44 
Objet: Re: [pve-devel] 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. 
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) 
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) 

(but you can convert raw to qcow2 also) 

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 ? 


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

De: "Dietmar Maurer" <dietmar at proxmox.com> 
À: "Alexandre DERUMIER (aderumier at odiso.com)" <aderumier at odiso.com>, pve-devel at pve.proxmox.com 
Envoyé: Vendredi 24 Août 2012 10:31:02 
Objet: VM snapshot problem 



>From what I see the following storage drivers provides internal snapshots: 

QCOW2 files 
sheepdog 
rbd 
nexenta (not fully functional) 

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)? 

But how can we handle LVM (lvm snapshots on shared storage does not work at all)? 

- Dietmar 



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Alexandre D e rumier 

Ingénieur Systèmes et Réseaux 


Fixe : 03 20 68 88 85 

Fax : 03 20 68 90 88 


45 Bvd du Général Leclerc 59100 Roubaix 
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-- 

-- 



	

Alexandre D e rumier 

Ingénieur Systèmes et Réseaux 


Fixe : 03 20 68 88 85 

Fax : 03 20 68 90 88 


45 Bvd du Général Leclerc 59100 Roubaix 
12 rue Marivaux 75002 Paris