Re: [Qemu-devel] [PATCH 0/7] block-vpc: Improve support for VHD images

[Jamie Lokier <jamie@shareable.org>]

Kevin Wolf wrote:
> This patch series improves the support for Virtual PC images. Until
> now, support for this image format is read-only and broken for large
> images. With these patches applied, you can create and write to VHD
> Dynamic Disks and some bugs in the read support are fixed. They have
> been tested with qemu-img convert from and to raw images and a
> successful openSUSE installation on a fresh VHD image.

Ooh, I look forward to trying these patches. :-)

I have some VHD image of Windows which always resulted in lots of
scandisk errors when Windows booted from it (using -snapshot), and the
same when converted to a QCOW2 file by qemu-img.

The only thing that worked was using MS VirtualPC's convert-to-raw
facility from the disk image wized, then I could use that raw file
with QEMU.  That proved qemu-img was getting it wrong.

(By the way, VPC took *ridiculously* long - about 8 hours for an 80GB
sparse image.  VirtualPC appears to use unbuffered writes (equivalent
to O_DIRECT) at least when over SMB, but they are small writes and not
overlapped, so it trickles along very slowly).

So I look forward to trying these patches on that image, which I don't
use know but kept for this very purpose, and seeing if it's fixed the
errors.

-- Jamie