Currently, the Bareos VMware Backup Plugin does not work on NFS datastore. It will fail with an error message similar to

Fatal error: Traceback (most recent call last):
...
msg = u'Error caused by file /vmfs/volumes/6c0378da-9f01ff6c/VMName/VMName.vmdk'
...


The reason is that the Bareos VMware Backup Plugin uses the special "*" change ID to query CBT information, but as of http://kb.vmware.com/kb/1020128 it is required that the virtual disk is located on a VMFS volume, backed by SAN, iSCSI, or local disk.

If the above error occurs when using a VMFS datastore on SAN, iSCSI, or local disk, it usually means that the CBT information must be reset by using vmware_cbt_tool.py (included in the bareos-vmware-plugin package) with the --resetcbt option or by manually following the instructions in http://kb.vmware.com/kb/2139574

Make sure to run a full level backup after resetting CBT, trying incremental will fail with a similar error in this case.