Backups of fault tolerant virtual machines fail with an "unable to create snapshot" error.
Creating snapshots of fault tolerant virtual machines is not supported within vSphere. Since creation of snapshots is a necessary condition of vRanger backups, backups of fault tolerant virtual machines is unsupported by vRanger.
Either break the fault tolerant set during the backup or do not attempt to backup the fault tolerant VM.
Please see VMware KB article 1016619 for more information: http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1016619
