Re: KVM management and API

[Anthony Liguori <anthony-rdkfGonbjUSkNkDKm+mE6A@public.gmane.org>]

Daniel P. Berrange wrote:
>> 5. Snapshots : where are snapshots saved ? I tried savevm with /tmp/x, I was expecting a 
>>    file containing memory image... do these work differrently ?
>>    Also, when one does loadvm, is the snapshot gone ? I mean can one restore the same 
>>    snapshot multiple times ?
>>     
>
> libvirt has APIs for snapshotting, but we've not implement them for QEMU
> or KVM yet. You can save the file to any location you have write permissions
> for. Its not a plain memory image because it also contains info about the
> state of all the various virtual devices.
>
> The snapshot doesn't deal with changes in state on your disks. So if you restored
> a snapshot, ran it for a while doing disk IO and then quit & tried to restore the
> snapshot again your disks would be out of sync.
>
> That said if one could take snapshots of the disks (eg with LVM, or QCOW) then
> it ought to be possible to use a snapshot multiple times over.
>   

With QEMU 0.9.0 (and by extension, KVM), snapshots are actually stored 
as part of the disk image with qcow2.  This allows you to have a 
consistent snapshot that includes CPU state and disk state.

Regards,

Anthony Liguori

> Dan.
>   


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