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

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)?