walt wrote:
Some background for my question: I've been trying to install
and then update Windows Vista using kvm. Everything works great
until I use 'qemu-img commit' to apply all the Windows Updates
to my original base install of Vista.
After doing the qemu-img commit step, the backing file is now
corrupt, 100% reproducibly. I don't have the same problem with
Windows XP, however, and I wondered if the problem is caused by
the sheer size of the commit that Vista requires.
When I install XP, then windows-update, and then qemu-img commit
the updates, I'm committing about 1GB of updates to a 3GB backing
file.
When I install Vista and then later commit the Vista updates, I'm
committing a 3GB file to a 6GB backing file, and that's when the
corruption happens every time.
So I tried an experiment with Vista -- I deliberately limit the
number of windows updates I allow at any one time, and then use
qemu-img commit after each small update. Voila, everything now
works perfectly -- no file corruption!
We've started getting some reports of corruption on "commit" in KVM.
There is a long standing disk corruption issue too that is very
difficult to reproduce. The thinking is that there is a bug somewhere
in the qcow2 code.
Is anyone actively looking into this?
Regards,
Anthony Liguori
And that's why I suspect there is a functional limit to the size
of each commit I can do with qemu-img.
Any thoughts or possible diagnostic maneuvers to be tried?
Thanks!
(BTW, I get the same results using 32-bit linux and 64-bit linux
on the same amd64 machine, using both gcc3 and gcc4.)
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