Re: [Qemu-devel] [RFC] qemu snapshot enchancement

[Paolo Bonzini]

Il 29/01/2013 14:27, Stefan Hajnoczi ha scritto:
>> > and in step 5, may need export the delta data, not the whole disk
>> > data.
> NBD doesn't have a way to perform bdrv_is_allocated().  Either we need
> to enhance the protocol or we need to add a QMP command to read
> the allocation bitmap for an image.  I'm a little hesitant about sending
> the bitmap or allocation extent information over QMP (JSON) but it might
> be doable.

I'm planning to add offline mirroring to qemu-img.  If you use an NBD
server as the destination, it can be used to send only the delta between
two snapshots via NBD.

I think this is the opposite of what you suggested, which is to run
qemu-nbd on the image and query the server.

Paolo