Re: Storing command line options in qcow2 images

Jorge Lucángeli Obes
2007-08-06T23:31:30Z

On 8/6/07, Anthony Liguori <anthony-rdkfGonbjUSkNkDKm+mE6A@public.gmane.org> wrote:
> I don't think adding annotations as snapshots is the right approach. I
> think proper support should be added in the header. I wouldn't be too
> concerned with breaking compatibility in qcow2. That's why it's qcow2
> and not just an updated version of qcow, qcow2 is still, AFAIK, open for
> breakage.

I think I'm fine either way. Avi suggested the snapshot-based
implementation so Laurent and I started working in that direction. We
are now close to finishing the basic functionality. That's not to say
that our solution should be accepted because it's almost ready. I
would like to reach consensus for the way in which all this should be
implemented.

The advantage of the snapshot-based approach is, as it has already
been discussed, its backwards-compatibility. I also think that it
requires less changes to the source code. I am not very familiar with
QEMU development so I'm not able to tell whether or not qcow2 is open
for breakage. I guess we decided to play it safe.

The header-based implementation would be conceptually easier of
course. It would have the added benefit of not having to deal with the
possible use of an empty snapshot (i.e., one with command line
options) in loadvm. That's the only thing left to fix in our current
implementation.

As I said, I'm fine either way. I have a final tomorrow, but after
that I will post our patches for review.

Cheers,
Jorge