If you are using HotAdd to backup VMDK disks which are larger then 2TB while running vSphere 5.5 be warned that this will fail silently as described in KB2068424.
- When using the HotAdd transport mode, you are unable to back up disks that are 2 TB or larger in size.
- Backing up disks larger than 2TB in HotAdd transport mode fail silently, but report a successful back up on Windows virtual machines.
VMware currently has no workaround for this! If you are using Veeam make sure you check out the solution provided by Luca.