Well, so I've blown away my first Windows install on the PV drivers. Big shock there.
The problem seems to have been that the same device was being enumerated as both a QEMU emulated device, and as a PV SCSI device. This led to immediate irreparable filesystem corruption. (Thanks, Microsoft, although truthfully I don't know if any of the Linux filesystems would have done better.)
Interestingly, this seemed harmless across several reboots as long as the backing devices were of type file:. In that situation, the PV device showed up in the disk manager, but wasn't mounted. (The INSTALL file with the PV drivers offers a clue: only phy: devices provide the right sort of hard-drive oriented metadata.) Only when I used the device mapper to access the files as physical devices did Windows automatically map a drive letter -- and incidentally destroy the filesystem.
Anyway, we have to get this working. I'm not ruling out failure as an option, but neither are we going to give up without throwing a truly herculean effort into the task. Windows is reinstalling now. I think I'll back it up this time before I do anything stupid.
The problem seems to have been that the same device was being enumerated as both a QEMU emulated device, and as a PV SCSI device. This led to immediate irreparable filesystem corruption. (Thanks, Microsoft, although truthfully I don't know if any of the Linux filesystems would have done better.)
Interestingly, this seemed harmless across several reboots as long as the backing devices were of type file:. In that situation, the PV device showed up in the disk manager, but wasn't mounted. (The INSTALL file with the PV drivers offers a clue: only phy: devices provide the right sort of hard-drive oriented metadata.) Only when I used the device mapper to access the files as physical devices did Windows automatically map a drive letter -- and incidentally destroy the filesystem.
Anyway, we have to get this working. I'm not ruling out failure as an option, but neither are we going to give up without throwing a truly herculean effort into the task. Windows is reinstalling now. I think I'll back it up this time before I do anything stupid.
Tip from the Computer Janitor: When doing development within a XenU, before you make changes that could break it, do
lvcreate -s -n backupDomU /dev/vgname/lvname -L 1024
it's instant, and allows you to roll back easily. if it turns out ok, just
lvremove /dev/vgname/backupDomU
(Uh, you can leave an arbitrary number of old snapshots around, but they cost in terms of disk performance, and
very bad things happen if they run out of space.)
to roll back:
dd if=/dev/vgname/backupDomU of=/tmp/backup
lvremove /dev/vgname/backupDomU
dd if=/tmp/backup of=/dev/vgname/lvname