[Libguestfs] Point-in-time snapshots (was: Re: Inspection of disk snapshots)

[Richard W.M. Jones]

On Fri, Mar 27, 2015 at 12:15:34PM +0000, Stefan Hajnoczi wrote:
> On Thu, Mar 26, 2015 at 12:02:27AM +0100, Kashyap Chamarthy wrote:
> > So, something like?
> > 
> >   . . .
> >   { 'execute': 'drive-backup', 'arguments':
> >         { 'device': 'drive-virtio-disk1', 'sync': 'full', 'target':
> >         'nbd://localhost', 'mode': 'absolute-paths', 'format': 'qcow2' } 
> >   . . .
> > 
> > Same question as yours, what is the NBD server going to run?
> > 
> > 
> > My only NBD testing so far has been with w/ NBD over Unix socket or
> > over TCP[**].
> 
> For 'sync': 'full' mode qemu-nbd or nbd-server can be used as the
> server.  You probably don't want 'format': 'qcow2', just raw data over
> NBD.  That way the NBD server can implement whatever storage backend it
> likes (raw, qcow2, something else).
> 
> For incremental backup the NBD server would either be a qemu-nbd
> instance with a qcow2 image and backing file:
> 
>   full-backup.img <- incremental-1.qcow2 <- incremental-2.qcow2
> 
> Or the NBD server would be a custom backup application that does
> something smart with the incoming NBD WRITE requests.

What I care about is connecting libguestfs to qemu and reading a
snapshot at some point in time, even though the guest is still writing
away to its disks.  Is this possible with drive-backup (or otherwise)?

Rich.

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