Backing Up Virtual Machines on CSV with Hardware VSS Providers, Set to Register KEY
If you are using a hardware VSS provider, you can back up multiple virtual machines from the same CSV/node in the cluster.
To allow a maximum of three backups to run concurrently on each node, specify the number of concurrent backups that can run from a node.
Set the following registry key:
HKLMSoftwareMicrosoftMicrosoft Data Protection Manager2.0ConfigurationMaxAllowedParallelBackups
Value Microsoft Hyper-V
Microsoft does not recommend that you do not use a value greater than 3 for optimal performance