Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format

[Kevin Wolf]

Am 10.09.2010 17:02, schrieb Anthony Liguori:
> What makes us future proof is having a good feature support.  qcow2 
> doesn't have this.  We have a good way at making purely informational 
> changes and also making changes that break the format.  Those features 
> are independent so they can be backported in a compatible way too.

I might have agreed that it's useful to be able to backport them
independently if we had had lots of such features added in the past. But
we haven't.

The qcow2 mechanism for compatible changes is header extensions (used
exactly once, for the backing file format) and for incompatible changes
increasing the version number (never used so far, if you consider qcow1
and qcow2 completely independent formats, which I think they are).

Kevin