Oliver Sommer 
2009-12-29
To limit a DPM server to just backup a certan number of VMs at a time you can add this registry key to the DPM server.
This will limit the number of parallel backups to the value entered:
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft Data Protection Manager\2.0\Configuration\MaxAllowedParallelBackups]
"Microsoft Hyper-V"=dword:00000001