Peter Seale's weblog

Monday, October 08, 2007 11:00:15 PM UTC 

Eulogy

SharePoint VM #3 lived a full life. A happy life.

But it was a short life. The SQL Server Express instance simply could not continue, and I made the difficult decision to put this to sleep. R.I.P., SharePoint VM #3.

What am I doing wrong?

I assume I'm doing something horribly wrong. I swear I'm not making any of the common mistakes, but let me enumerate the facts just in case:

• I store the VHD (hard drive), VMC (configuration file) and presumably the RAM file all on a single external hard drive.  This is dangerous but is a giant performance boost over running the VHD on the same spindle as the OS. No, I'm not some kind of OS guru, but this is common wisdom.
• I use Virtual Server to run my VM.
• I make sure to "Shut Down" the VM before leaving each day.
•  I use the Windows "remove external hard drive" tray icon every time before unplugging the hard drive. This is crucial as my external hard drive is (presumably) running on an NTFS partition, and unwritten delayed writes are a big potential source of corruption.
• I use VPC to run this VM from another computer. This should not be a problem.

What I refuse to do is enable Virtual Server's "undo disks" feature. Undo disks allow you to write all hard drive changes separately from the VHD file, thus allowing you to "undo" any changes you may have made. Basically, I could "revert" the undo disk any time I face corruption.

Undo disks take forever, literally forever, to merge your VHD with all the journaled changes. Forever! For daily, non-demo use, this 15-minute-plus delay is onerous. If I seriously needed undo disk features, I'd use VMWare instead—I've been told it's worlds faster and supports "branching" of VM changes.

VMWare is not an option at this time.

What I learned - VM backup strategy

This has renewed my dedication to have a solid backup plan for my VMs:

1. Store my SharePoint development work outside of the VM. In my case, I keep all assemblies in a Subversion repository on my host machine, and store a daily "stsadm -o export" site backup on the host PC. I will further note that I additionally backup the files from the host PC to another PC, thus eliminating my host PC as a point of failure.
2. Take a weekly backup of my VM's hard drive (VHD) file. This takes 15 minutes to complete, after I've turned the VM off, meaning no VM work may be done during this time. This has saved me heaps of time already.
3. Store an old VHD backup offsite. Define "offsite" yourself; whether "offsite" is your host computer's hard drive, or a file server at work, or burned to a DVD, the point is: it's stored somewhere away from the portable hard drive.