Tuesday, August 09, 2011

FreeBSD 8.1, 8,2 and Hyper-V R2 SP1 Install Problem - Use Fixed Size VHDs

Just tried installing FreeBSD 8.1 and 8.2 virtual machines on a Windows Server 2008 R2 Core install with the Hyper-V role installed and with SP1 applied. newfs created the file systems just fine, but the distribution unpacking would cause random kernel panics, throwing ‘ufs_dirbad: bad dir ino XXX at offset XXX: mangled entry’ errors.

I’d created the VHDs as dynamically sized VHDs. I blew these away and created fixed size VHDs and attached them to the VMs. I’ve been repeatedly performing full distribution installs without error. I managed to find a Hyper-V R2 box without SP1 and couldn’t replicate the install problem with dynamically sized VHDs, so Microsoft have introduced a problem with SP1.

If you’re seeing disk-related problems with your UNIX/UNIX-like VMs on Hyper-V, check to see if you’re using dynamically sized VHDs and convert them to fixed size VHDs to see if this fixes the problem.


Anonymous said...

Apparently this is a problem with the disk size, not fixed/dynamic. Something goes wrong in FreeBSD if it sees a Hyper-V disk larger than 40GB.

Chris Knight said...

Thanks for the feedback, but when I did this I was using 20GB disks and I've got a repeatable test scenario. Failure occurs on dynamic sized disk but not on fixed size disk.