[PVE-User] V4.1: "Move Disk" function leads to file system corruption

Stefan Plattner stefan at ssl.sepa.ws
Wed Mar 9 19:14:25 CET 2016

Hello everyone!

I used the "Move Disk" function in the "Hardware" tab of a 
stopped/offline Windows-VM. After the process was finished, I re-started 
the VM and the Guest greeted me with the following, in this cas 
SQLServer related, (fatal) error message:

"Could not open error log file Operating system error = 1392"

Running a chkdsk inside the VM revealed several files system errors but 
even after "chkdsk /f", SQLServer still fails to start with "sql server 
error 9004"...

Switching back to the original disk (raw format), resolves all this 
filesystem problems and SQLServer starts fine. No disk problems reported 
with chkdsk (in the guest).

Examining what is happening when executing a "Move disk", ps revealed 
the following command line:

"/usr/bin/qemu-img convert -t writeback -p -n -f raw -O raw 

So what seems to happen, is not a simple fs move/copy, but a conversion 
from raw to raw...
The resulting file is also different from the original:
"cmp /mnt/pve/prox02-ssd-lv/images/501/vm-501-disk-2.raw 
vm-501-disk-2.raw vm-501-disk-3.raw differ: byte 1228841, line 737"

I don't understand why a "convert" is happening at all (same image 
format) but the at the moment the result is a binary different image 
which is causing fatal filesystem errors in the (Windows) guest.

When I simply copy (cp) the disk to the new directory, the files are 
(thank god) identical and everything is working fine. If I use the "Move 
Disk" feature, I end up with a corrupted filesystem in the guest.

Am I missing something fundamental, am I doing something wrong or is 
this a well known or new bug/problem?

Thank you for your advise, the problem is reproduceable on my system!

Best regards, Stefan

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