I noticed our backup server was failing to hot add disks during the backup process – ultimately leading to incredibly slow backup times. The backup job would not report any progress, and eventually would fail over to network mode.
The backup server is a VM, and the transport mode is Virtual Appliance. After testing the hot add procedure myself using snapshots, and mounting the base disk to the backup server, this confirmed hot add functionality.
The automount feature of a Windows server needs to be disabled in this case, and a scrub was necessary to clear out assigned drive letters of any previously connected disks. We also want to prevent any previously connected disks from auto mounting when they are connected again.
To perform these steps, type the following into a command prompt:
diskpart automount disable automount scrub
Then, try to run the backup job again. It should have hot add functionality again. If it still doesn’t work, you can try checking the registry key:
When all else fails, rebuild your Veeam server and restore it’s config.