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

[Paolo Bonzini]

Il 29/01/2013 17:44, Stefan Hajnoczi ha scritto:
>> >
>> > 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.
> Yep, exactly.  The nice thing about your approach is that we don't
> need an explicit API for dirty block tracking, it's implicit in the
> writes that we send to the backup application's NBD server.

Of course the ugly thing is that it is much less flexible than letting
the backup application do its own thing.  Also, there is just one dirty
bitmap that you need to use for everything, though in the future the
"block filters" patch will come up magically and will let you have
multiple dirty bitmaps...

Paolo