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

[Dietmar Maurer]

> > > We track zero blocks at 4KB level to get small backup files. Restore
> > > can handle those blocks differently, either pre-allocate or create
> > > holes. That
> > can even be a restore option.
> >
> > You are right, the behavior can be set at restore time.
> >
> > I'm curious how much of a win the 4 KB zero detection is on random
> > Linux or Windows guest images.  Have you collected numbers?
> 
> Well, seems that it does not help much - it saves about 0.2% space. So maybe
> we can remove that feature (and increase address space in the VMA format
> instead).

Sorry, I need to correct myself - I had a bug in the code. 

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.