Take care when backing up vmdk disks > 2 TB with HotAdd (vSphere 5.5)

If you use vmdk disks with a size of 2 TB or larger and use HotAdd mode to do backups, please take care and read VMware’s KB 2068424.

There is a known issue affecting the Virtual Disk Development Kit (VDDK) 5.5. Your Backup will report a successful backup, but in real it fails silently.

Currently there is no workaround or resolution available from VMware.

If you use IBM Tivoli Data Protection for VMware you can try to change the transport mode (but please check twice if the workaround is working in your environment!):

Create a dedicated Backupjob for the affected virtual machines and define the transport mode in the dsm.opt file.

With the following command, SAN is the prefered transport mode. If SAN is not available, NBD will be used, but not NBDSSL or HotAdd:


If you use Veeam Backup and Replication take a look at the post from Luca Dell’Orca (virtualtothecore) – he descripes a workaround you can try.

Leave a Comment

Your email address will not be published. Required fields are marked *