Re: Storing command line options in qcow2 images

Avi Kivity
2007-08-08T00:15:18Z

Daniel P. Berrange wrote:
> On Tue, Aug 07, 2007 at 07:10:17AM +0300, Avi Kivity wrote:
>
>> Anthony Liguori 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.
>>>
>>>
>> Are all the users' images open for breakage too?
>>
>
> I'd say not. QCow2 has been around for a long time now so breaking compat
> with existing images would be a very bad idea. Ideally though some extension
> would be both backwards & forwards compatible - eg existing qcow2 impls
> would just ignore any new extension, while new impls would work any image
> with or without extension. If this isn't possible then at least call any
> new format qcow3 to make it obvious to users that it is not compatible.
>

It was, of course, a rhetorical question. I initially suggested using a
special snapshot as a means of preserving compatibility with qcow2,
which I think is better than introducing yet a new format.