Re: [Qemu-devel] Re: KVM call agenda for Oct 19

Anthony Liguori
2010-10-19T13:22:20Z

On 10/19/2010 07:48 AM, Dor Laor wrote:
> On 10/19/2010 04:11 AM, Chris Wright wrote:
>> * Juan Quintela (quintela@redhat.com) wrote:
>>>
>>> Please send in any agenda items you are interested in covering.
>>
>> - 0.13.X -stable handoff
>> - 0.14 planning
>> - threadlet work
>> - virtfs proposals
>>
>
> - Live snapshots
> - We were asked to add this feature for external qcow2
> images. Will simple approach of fsync + tracking each requested
> backing file (it can be per vDisk) and re-open the new image would
> be accepted?

I had assumed that this would involve:

qemu -hda windows.img

(qemu) snapshot ide0-disk0 snap0.img

1) create snap0.img internally by doing the equivalent of `qemu-img
create -f qcow2 -b windows.img snap0.img'
2) bdrv_flush('ide0-disk0')
3) bdrv_open(snap0.img)
4) bdrv_close(windows.img)
5) rename('windows.img', 'windows.img.tmp')
6) rename('snap0.img', 'windows.img')
7) rename('windows.img.tmp', 'snap0.img')

Regards,

Anthony Liguori

> - Integration with FS freeze for consistent guest app snapshot
> Many apps do not sync their ram state to disk correctly or frequent
> enough. Physical world backup software calls fs freeze on xfs and
> VSS for windows to make the backup consistent.
> In order to integrated this with live snapshots we need a guest
> agent to trigger the guest fs freeze.
> We can either have qemu communicate with the agent directly through
> virtio-serial or have a mgmt daemon use virtio-serial to
> communicate with the guest in addition to QMP messages about the
> live snapshot state.
> Preferences? The first solution complicates qemu while the second
> complicates mgmt.
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