Re: [Qemu-devel] [PATCH v4 0/6] Efficient VM backup for qemu

[Stefan Hajnoczi]

On Fri, Feb 22, 2013 at 11:39 AM, Kevin Wolf <address@hidden> wrote:
> Am 22.02.2013 um 11:31 hat Stefan Hajnoczi geschrieben:
>> On Thu, Feb 21, 2013 at 03:56:15PM +0000, Dietmar Maurer wrote:
>> > > On Wed, Feb 20, 2013 at 04:04:49PM +0000, Dietmar Maurer wrote:
>> I added the 'wait-for' attribute which tells QMP transaction to let the
>> migration action complete first before doing the backup block job.  This
>> way we first live migration VM state to vmstate.bin and then atomically
>> kick off the backup block job - with consistent disk state.
>
> I'm not sure if this really belongs in qemu. The management tool can
> wait for the migration completed event, after which the VM will be
> automatically stopped, do the snapshot and then continue the VM. This
> is, as far as I know, the approach that libvirt takes today.

Good point, this is smarter and exists today.  Issue a 'migrate'
command first and wait for the completion QMP event.  Then issue the
'transaction' command while the guest is still paused (== consistent
snapshot at point in time when migration/savevm completed).

Stefan