Re: [Qemu-discuss] Live VM backup

[Vincenzo Romano]

2017-08-30 10:53 GMT+02:00 Fam Zheng <address@hidden>:
> 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

I understand.

So, if I haven't miunderstood, at the moment QEmu-KVM doesn't
implement  "VM snapshots".

Thanks a lot for the insights.

-- 
Vincenzo Romano - NotOrAnd.IT
Information Technologies
--
NON QVIETIS MARIBVS NAVTA PERITVS