Working with backup sets : VMware VADP backup sets (Windows or Linux) : Limitations for VMware VADP backup sets
 
Limitations for VMware VADP backup sets
The following limitations apply to VMware VADP backup sets:
You cannot back up virtual machines that have Fault Tolerance turned on. For more information, see “Backup of fault tolerant virtual machines”.
You cannot back up virtual machines with physical or virtual raw disk mapping (RDM) devices.
Avoid running multiple clones with Local DS-VDR activities on the same virtual machine from the same or different Local DS-VDR Tools.
Avoid scheduling or performing VMware VADP backup and VMware vSphere snapshot replication activities at the same time on the same vSphere virtual machine. Doing so can adversely affect the backup or replication process.