Tuesday, February 28, 2012

Hyper-V Lab Experiment; Attack of the Snapshots

DeLorean time machineThis is a brief chronicle of the effect of re-creating a Virtual Machine from a Virtual Hard Drive that had Snapshots taken and not merged back into the parent image.


In August 2010, I created a Hyper-V lab with a Windows 7 development VM and a Server 2008R2 testing VM. The VM hard disks, virtual machines, and snapshots were stored on the SATA hard disk. The Hyper-V Server 2008R2 host was installed on a bootable USB pen drive.

Apparently around November 2010 and over the course of 2011 I created a few snapshots of the Windows 7 VM.

Fast forward to a couple weeks ago

My Hyper-V environment lost power and when it restarted the BIOS failed to recognize the Kingston USB pen drive that Hyper-V was booting from. Result: My lab was down. This happened one other time, but after some fiddling with the BIOS, I  was able to get the USB drive to be recognized.

In order to prevent this from happening in the future, I replaced the USB pen drive by installing Hyper-V Server 2008R2 on an IDE drive, plugged it into my lab box and booted. I created a new Virtual Machine using the existing Window 7 Virtual Hard Drive and powered up my development VM. Upon a quick glance everything looked fine.

Missing Files and Programs

A few days later while logged into my Dev VM, I noticed several of my files and directories were missing, Microsoft Office wasn’t installed, and SQL Server said the trial had expired. What?!?

A quick check of the Windows Event log and there was an entry that Windows was not shut down properly on November 11, 2010, but was back up and running on Feb 12, 2012. Suddenly I was missing over a year of development activity; not really. 

Don’t Panic!

November 11, 2010 was the date the first snapshot was taken. All the activity since then was in the snapshot differencing disks (3 files with a .AVHD extension).

I had a Windows Image Backup and regular full backups, but instead of restoring from backup, I decided to have a little fun with the Hyper-V management console instead.

A little research and I found this article about merging differencing disks. It isn’t the best reference you can find because it doesn’t have screenshots of the process like this one. I actually backed up the parent VHD and child AVHD files and renamed the AVHD files VHD, but it appears the renaming process is unnecessary. Otherwise after using the Hyper-V management console to merge each of the AVHD files to their parent drives, I powered up the dev VM after merging and everything was back to the state prior to the initial power outage. Success!

Moral of the Story

If you use a Hyper-V snapshot to test a Windows Update or some other configuration change that you want to be able to roll back out of, make sure to merge the snapshot back into the VM. Don’t leave it in a snapshotted state. Especially not with multiple active snapshots.

Reference: Hyper-V: Avoid using differencing disks on virtual machines that run server workloads in a production environment.

photo credit: pnoeric / CC BY-SA 2.0

Thursday, February 16, 2012

Error 2337 Installing SQL Server 2008R2 in Virtual PC 2007


Last year I was preparing for an fwPASS presentation on Report Viewer 3.0 by installing SQL Server 2008R2 in a virtual machine using Virtual PC 2007. I kept getting an error 2337 indicating that the disk may have been corrupt or damaged. I was installing it from a .iso image I downloaded from my MSDN Ultimate subscription. I used the Virtual PC “capture iso image” functionality to mount the iso as a disk. I downloaded another copy of the iso image and repeated the process with the same results. Due to time constraints, I reverted back to SQL Server 2005 and Report Viewer 2.0 for that presentation, highlighting features new to 3.0 using screenshots.

Physical and Hyper-V Success

Since then I have successfully installed SQL Server 2008R2 successfully multiple times on bare metal physical servers and in VM’s using Hyper-V Server 2008.

VPC Still an Issue

Fast forward to this week. I was setting up a development sandbox in a VM. Again I was installing SS2008R2 by mounting the image in VPC 2007 and was faced with the same Error 2337. Seriously? This issue hasn’t been resolved yet? A quick search on the error resulted in this helpful post Getting error 2337 installing SQL Server on a VPC on the SQL Skills blog.


I didn’t have any blank DVD’s on hand for burning the image, so I decided I would use MagicDisc to mount the iso file on my host machine, instead of using VPC’s capture iso functionality. That solved the problem.