On 09/10/2010 06:25 AM, Avi Kivity wrote:
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).
It's actually pretty easy in QED and it should perform very well.
http://wiki.qemu.org/Features/QED/Trim
Regards,
Anthony Liguori
