Hello Tom, here is the list:
• Hot Add transport may fail while mounting large (1 TB) VMDK files.
• LUN with Veeam Backup server is located should have capacity more than (or equal) the capacity of the disk which is being hot added. Actual free space can be less than hot added virtual disk size.
• Hot Add transport is not supported for backup server VM with IDE virtual disks. Use SCSI virtual disks instead.
• Hot Add transport is not supported for backup server VM with SAS adapters.
• Hot Add may fails if Veeam Backup VM has one of the following configurations:
- The proxy virtual machine on ESX 4.x has an IDE disk attached at IDE 0:0 and IDE 1:0.
- The proxy virtual machine does not have any IDE CD-ROM device.
• LUN where Veeam Backup VM resides should be formatted with proper block size to be able to mount the largest virtual disk of the hot added VMs.
1MB block size – 256GB maximum file size
2MB block size – 512GB maximum file size
4MB block size – 1024GB maximum file size
8MB block size – 2048GB maximum file size
• Hot Add and SAN transport fail, falling back to NBD transport, when a backed-up virtual machine has independent disks.
• With Hot Add transport, backup of a virtual machine fails when multiple disks have the same name, as they could if on different datastores.
• A single SCSI controller can have a maximum of 8 disks attached. To run multiple concurrent jobs with more than 8 disks, you should add more SCSI controllers in your Veeam Backup VM virtual hardware.
• In case of standalone host connection (no vCenter presented), you can only hot add VMs which are located on the same host running Veeam Backup VM.
• Virtual Appliance backup job fails after you’ve cloned or restored your VBR server. The reason for that is missing UUID for Veeam Backup VM virtual machine on the ESX server. Please refer to this KB article
for the instructions on fixing the issue.