Re: kvm on Ubuntu 8.04 running windows xp sp3: corrupts file system on shutdown?

[Yaniv Kaul <ykaul@redhat.com>]

On 7/2/2009 6:50 PM, Jon Watte wrote:
> I'm attempting to set up a Windows XP virtual machine using KVM
> running on 8.04 LTS x64 or a Core 2 Duo (6550). I have updated all
> installed packages to the latest available as of a week ago. This is
> KVM version 0.9.1 (kvm-62) on a kernel version 2.6.24-22-server.
>    
I warmly suggest updating to a later, much newer, KVM version. 
Specifically qcow2 format had corruption bugs similar to what described 
below.
Y.

> I'm creating a 20 GB hard disk image with qemu-img, (on a file system
> that is managed by LVM, and in turn backed by a md0 soft mirror) and
> then starting the VM as follows:
>
> #!/bin/sh
> cd /var/kvm/wxp_build
> kvm -m 1024M \
> -hda wxp_build.img \
> -usb -usbdevice tablet \
> -vnc :1 \
> -localtime \
> -net nic,model=virtio -net user \
> -redir tcp:5555::5555 \
> -daemonize \
> $*
>
> When I install, I pass "-cdrom ../cdrom/wxp_sp3_installer.iso -boot d"
> to boot from the Windows install CD. The reboot as part of the install
> does not take down the VM, and does not cause any problems.
>
> I can go through install just fine. I format the 20 GB image as NTFS,
> using slow format (not quick format).
>
> I can download and install other things fine, too. However, when I
> shut down the virtual machine (using the Windows Shut Down command),
> and wait for the VNC connection to end, the (virtual) hard disk seems
> to get corrupt. When I boot again, one of three things happen:
>
> 1) The boot fails, because some necessary file has gotten corrupted.
>
> 2) The boot succeeds, but when I attempt to run something that I
> installed that worked fine before the shutdown, it doesn't work after
> the shutdown, with missing DLL errors or similar.
>
> 3) The boot kicks into CHKDSK, which finds tons and tons of NTFS file
> system corruption on the virtual hard disk image.
>
> I've tried with both qcow2 and raw disk images, with the same results.
>
> To my mind, it behaves as if the KVM process decides to exit as soon
> as the BIOS power-off signal comes, but the process keeps the hard
> disk write buffer in user-mode RAM, rather than immediately having
> passed it on to the kernel. Thus, when the process exits, whatever was
> buffered will not be committed to disk, and badness ensues. I'm not
> sure at all that this is what actually happens, but that's what it
> feels like. It could be some other kind of image corruption, too, but
> it's clearly related to actually powering off the virtual machine.
>
> Btw: the same corruption happens if I kill the KVM while it's running
> (rather than do a "clean" shut-down). It's slightly more
> understandable under that situation, but not really -- NTFS is a
> journaling file system, and never has those corruption issues on my
> "native" Windows machines, even during power fail.
>
> So... does anyone have a clue what could be causing this, and what I
> can do to fix it?
>
>
>
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