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

[Avi Kivity]

 On 09/10/2010 02:14 PM, Avi Kivity wrote:
> > qcow2 is not a properly designed image format.  It was a weekend 
> > hacking session from Fabrice that he dropped in the code base and 
> > never really finished doing what he originally intended.  The 
> > improvements that have been made to it are almost at the heroic level 
> > but we're only hurting our users by not moving on to something better.
>
> I don't like qcow2 either.  But from a performance perspective, it can 
> be made equivalent to qed with some effort.  It is worthwhile to 
> expend that effort rather than push the burden to users. 

btw, despite being not properly designed, qcow2 is able to support 
TRIM.  qed isn't able to, except by leaking clusters on shutdown.  TRIM 
support is required unless you're okay with the image growing until it 
is no longer sparse (the lack of TRIM support in guests make sparse 
image formats somewhat of a joke, but nobody seems to notice).

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.