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

[Anthony Liguori]

On 10/19/2010 07:48 AM, Dor Laor wrote:
> On 10/19/2010 04:11 AM, Chris Wright wrote:
> > * Juan Quintela (address@hidden) 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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