I just noticed this new KB article:
Diskeeper is a 3rd party defragmentation product that has the ability to defragment unmounted NTFS volumes that are presented to the VMware Consolidated Backup proxy. This means that it can defragment RDM LUNs. Unfortunately, this creates the possibility of inconsistencies in the file system if there is a virtual machine running on that RDM.
The Automatic Defragment option causes the defragmentation to take place.
Consult your Diskeeper documentation to obtain instructions for disabling this feature in the version of the product that is installed on the VCB Proxy server.
Be aware to not use Diskeeper on your VCB proxy!
Also be aware of Diskeeper when a snapshot is active! The Automatic Defragment option causes snapshots to grow.