Re: [Qemu-devel] Re: Strategic decision: COW format

[Anthony Liguori <anthony@codemonkey.ws>]

On 02/18/2011 02:49 PM, Kevin Wolf wrote:
> Am 18.02.2011 20:47, schrieb Anthony Liguori:
>    
>> On 02/18/2011 01:11 PM, Kevin Wolf wrote:
>>      
>>>> A new file format like fvd would be a challenge for the existing ones.
>>>> Declare its support as unsupported or experimental, but let users
>>>> decide which one is best suited to their needs!
>>>>
>>>>          
>>> Basically this is what we did for QED. In hindsight I consider it a
>>> mistake because it set a bad precedence of inventing something new
>>> instead of fixing what's there.
>>>        
>> I don't see how qcow3 is fixing something that's there since it's still
>> an incompatible format.
>>
>> It'd be a stronger argument if you were suggesting something that was
>> still fully compatible with qcow2 but once compatibility is broken, it's
>> broken.
>>      
> It's really more like adding an incompatible feature flag in QED. You
> still have one implementation for old and new images instead of
> splitting up development efforts, you still have all of the features and
> so on.

In theory.  Since an implementation doesn't exist, we have no idea how 
much code is actually going to be shared at the end of the day.

I suspect that, especially if you drop the ref table updates, there 
won't be an awful lot of common code in the two paths.

Regards,

Anthony Liguori

>   It's a completely different story than QED.
>
> Kevin
>