IBM® Tivoli® Storage Manager was unable to obtain Changed Block Tracking(CBT) data for the specified virtual machine because changed block tracking is not supported. RDM disks in physical mode, virtual disks attached to shared virtual SCSI bus, and VMs with hardware version 6 or earlier are not supported. The backup continues, but instead of backing up just the used blocks (in the full VM backup case), or just the changed blocks (in the incremental VM backup case), the entire virtual machine is backed up. This backup includes both the used and unused blocks of the disk.