Today I decided to test out the Volume Shadow Copy (VSS) support in Virtual Server 2005 R2. In theory, as I mentioned in an earlier post, with VSS, virtual server can create a consistent “snapshot” of a running virtual machine so other applications, such as backup clients, can use that snapshot without interrupting the virtual machine itself.
The only VSS-aware backup application I had installed was Windows’ very own NTBackup. So, I enabled VSS on the volumes, run NTBackup, and proceed to make a backup of my virtual machine. Everything started out OK, until NTBackup got stuck with the message “Waiting to retry shadow copy…”. Following my standard error-solving checklist, I checked the Event Viewer, and I found this message logged:
Volume Shadow Copy Service error: Error calling a routine on the Shadow Copy Provider {f5dbcc43-b847-494e-8083-f030501da611}. Routine details BeginPrepareSnapshot({f5dbcc43-b847-494e-8083-f030501da611},\\?\Volume{0cb1b616-8ea6-11db-88de-806e6f6e6963}\) [hr = 0x80070002].
We use Acronis imaging solution for deploying our server, and it turns out that Acronis’ VSS Provider has an issue with Microsoft’s VSS provider. Apparently the issue is well-known, and is documented in two forums posts. It is solved in the latest version of Acronis’ products, but I didn’t really had time to perform an upgrade (and Acronis’ products are notoriously stubborn when you try to uninstall them). So, I applied the solution suggested in one of the forum posts. I unregistered Acronis’ VSS provider using the command:
regsvr32 /u \windows\system32\snapapivss.dll
After that, the backup went without problems:
Opening up the log once the backup is complete shows you that all files from the virtual machine were backed up succesfully:
This was done without turning the virtual machine off, taking advantage of the VSS functionality in Virtual Server 2005 R2 SP1 Beta. I performed the same operation on a Windows XP box, disabling NTBackup’s VSS support, and the backup predictably failed.
Here’s some information on VSS: Volume Shadow Copy Service (VSS)