Re: [Qemu-devel] [RFC 0/8] block: Live backup prototype

[Dietmar Maurer]

> > I can see space reduction up to 4% using this feature. Considering the
> > fact that it comes at no cost, it would be stupid to remove it.
> 
> Okay, looks like it's useful but not a huge win.
> 
> In the NBD approach pipelining writes (or discards) ought to make 4 KB zero
> blocks usable without overhead.

But you need to re-asemble 64KB block from that - I guess that is the difficult 
part here?