- Posted by ploft on March 31, 2009
Admitted, this is not my favorite solution to this problem, but if the alternative is no backup at all, this is without doubt a workable resolution.
In our setup I've experienced backup problems when using DPM 2007 to backup some of my VM's running on our Microsoft Virtual Server 2005 host. More specific these the errors appearing:
DPM 2007 reported:
The replica of vm-client-001 on vm-host-xxx.local is inconsistent with the protected data source. All protection activities for this data source will fail until the replica is synchronized with consistency check.
DPM encountered a retryable VSS error.
Microsoft Virtual Server 2005 host reported:
(Both visible in Event log and Virtual Server 2005 R2 master status webpage)
The VSS writer for Virtual Server failed during the PostBackup phase, during the mounting of disk \\?\GLOBALROOT\Device\HarddiskVolumeShadowCopy290\Virtual Servers\vm-client-001.vhd for virtual machine vm-client-001. The disk did not come online within 5 minutes. Confirm that the vhd mount driver in installed correctly and is able to mount virtual hard disks.
It's worth mentioning the VM, DPM has been failing to backup of the type: Online backups. I have several other VM's setup on the VM-host, without backup problems, both Online and Offline backups.
My way of fixing the issue with DPM continuing to fail when backup is initiated is solved by changing the backup-mode from Online backup to Offline backup. This is done by the registry on the physical/host machine running the VMs.
1. Open Registry Editor/regedit
2. Navigate to "HKEY_LOCAL_MACHINE\Software\Microsoft\Virtual Server\1.0\Backup\BackupType"
3. Either change the existing REG_DWORD-record if your VM is located here, or create a new REG_DWORD with the same name as your VM appears in Virtual Server 2005 R2 web-interface.
4. Set the value of appropriate record to: 1 This would changes the Backup mode to Offline backups.
Just for the kicks, here is the value definitions:
0/1: Offline backup
2: Online backup
Beware that DPM still reports it's as a Online Backup, but underneath the bonnet, it is Offline backup, and your DPM should no longer experience the mentioned problem. It's by the way not necessary to reboot any of the machines involved for the changes to take effect.