Re: [Qemu-discuss] Live VM backup

[Fam Zheng]

On Wed, 08/30 08:17, Vincenzo Romano wrote:
> Il 30 ago 2017 05:19, "Fam Zheng" <address@hidden> ha scritto:
> 
> On Tue, 08/29 18:32, Vincenzo Romano wrote:
> > I'd like to move away from "another virtualization solution" to QEmu.
> > I've more or less all the needed bits in my hands in order to define,
> > run and manage QEmu VMs.
> > What I am missing is the knowledge of how to backup a live VM.
> > Of course, if I shutdown the VM, I can simply copy its files and the
> > startup script on another QEmu host.
> > But my main objective is to do the backup while the VM is running.
> > I think I could use the snapshot feature, but have no idea on how to
> proceed.
> > Any hint?
> 
> In short, just do what libvirt would do: use QMP and send 'drive-backup'
> command.
> 
> This is a very good howto:
> 
> https://github.com/qemu/qemu/blob/master/docs/interop/live-b
> lock-operations.rst
> 
> Fam
> 
> 
> Thanks.
> I presume there's a 'drive-restore', though I need to look better in the
> docs.
> 
> Is there any side effect in case the CPU where the VM will be restored is
> not exactly the same as the one where the VM got backed up?

No, there isn't a 'drive-restore'. 'drive-backup' only takes care of the disks,
so the CPU, ram and device states aren't saved.

If you boot from the backup image, CPU and ram are restarted from powered off
state, so what happens is effectively like a power loss at the point of
'drive-backup': anything not saved to disk are lost.

Fam