> > Does this only work for qcow2 images, or will it also work for LVM images?
>
> If your root backing file is raw (I tested this just now, again) or LVM,
> it should work just fine.  And the overlays will _have_ to be qcow2
> files.

All my VM images are raw format on LVM volumes (hope I'm using the right terminology here). I don't use backing/overlay images. So  this should work for me.

I currently use LVM snapshots as part of my backup process. Does anyone see any pros and cons of the active block commit method in this thread vs using LVM snapshots (which are very quick to create)?