[pve-devel] Fwd: qemu-rbd : savevm monitor command don't save vmstate, is it normal ?

Alexandre DERUMIER aderumier at odiso.com
Wed Aug 29 18:30:53 CEST 2012

reponse for josh, rbd don't support save of the vmstate for now.

----- Mail transféré ----- 

De: "Josh Durgin" <josh.durgin at inktank.com> 
À: "Alexandre DERUMIER" <aderumier at odiso.com> 
Cc: ceph-devel at vger.kernel.org 
Envoyé: Mercredi 29 Août 2012 18:15:17 
Objet: Re: qemu-rbd : savevm monitor command don't save vmstate, is it normal ? 

On 08/29/2012 06:40 AM, Alexandre DERUMIER wrote: 
> Hi, 
> I'm trying to take a full vm state snapshot with savevm monitor command (qemu 0.12rc1 + rbd 0.48.1) 
> it seem that vmstate is not saved in the snapshot. (I also don't notice any vm hang during snapshot) 
> Snapshot of disk is correctly made. 

AFAIK the only block backend that supports saving the vmstate is qcow2. 
For rbd, the savevm/loadvm monitor commands are equivalent to 
'rbd snap create' and 'rbd snap rollback'. They just save/rollback the 

> using loadvm monitor command, rollback correctly to disk snapshot but vm hang. 

If you don't quiesce i/o i.e. via xfsfreeze (it works on the vfs level 
now, so it's not xfs-specific anymore) before snapshotting a running 
vm, the fs might require a fsck to be usable. This is only rolling back 
the disk, and not the memory state, so doing it while the vm is running 
is likely to cause problems. 

> starting qemu with -loadvm snapshotname give 
> kvm: Error -22 while loading VM state 
> Is it normal ? Not implemented ? 

bdrv_{save|load}_vmstate are not implemented. 

> Regards, 
> Alexandre 




Alexandre D e rumier 

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