On Tue, Aug 12, 2014 at 10:07 AM, Eric Blake <eblake@redhat.com> wrote:

> On 08/12/2014 07:45 AM, 吴兴博 wrote:
>
> [please don't top-post on technical lists]
>
> Sorry about that..

>  > Thanks for your information. It's really helpful.
> > I think adding a bitmap alongside the raw file ( or just within that
> file)
>
> Umm, how do you propose to add a bitmap within a raw file?  The moment
> the file contains metadata, it is no longer raw, but some other format.
>  You'd need a way to reliably delineate the portion of the file that
> contains the bitmap and therefore must not be exposed to the guest.
>
> Yes a agree. It's not raw anymore. It should be some 'lightweight' format.

 > would be suffice to distinguish between present or in backing file.
> > The idea in FVD looks similar to 'addcow'---use bitmap but delegating
> > allocation to FS. However FVD seems to have been ignored by community.
>
> Care to give a pointer to a URL describing the FVD format?
>
> http://lists.nongnu.org/archive/html/qemu-devel/2011-01/msg00398.html

This thread could be the clearest message on FVD.
It also has a paper published on USENIX conference.
https://www.usenix.org/event/atc11/tech/final_files/Tang.pdf

> --
> Eric Blake   eblake redhat com    +1-919-301-3266
> Libvirt virtualization library http://libvirt.org
>
>