I just re-read your post,
Gostev wrote:With HotAdd transport, full backup of a virtual machine fails when multiple disks have the same name, as they could if on different datastores.
The C:\ and the D:\ are on separate datastores, they probably both have the same .VMDK name. So that could be part of it as well, although we are still up against the 1TiB limit on that machine. I'm going to re-do that to a 750TiB drive this weekend and see if that helps. The other machine, though, is all on the same datastore, so it definitely has different .VMDK names, and my Exchange is on 3 separate data stores (C:\, D:\Mailstores, E:\Logs) for performance. That has backed up with VA/HOTADD all week, it only failed last night.
It's strange for sure! But now @benmilligan is following the case, assisting the tech that is assigned to it, so hopefully with his coaching her, things will move along...
For every expert there is an equal and opposite expert - Arthur C Clarke's Fourth Law