Using qcow2 with NBD

Pro	Matches existing use Server can start with thin qcow2, and grow it as needed with guest activity	Guest-visible size can be changed Backing files Dirty bitmap tracking Any other qcow2 features...
Con	Guest size is fixed No access to qcow2 features from client	Server file must be preallocated, or else guest hits ENOSPC Internal snapshots are unlikely to work

Can we merge the best of both worlds, giving the client access to all qcow2 features, but permitting resize of the underlying file on the host?

Clipart of computer http://clipart-library.com/clipart/76irEkBcK.htm