I know the documentation says a physical server is required for VCB. Is this requirement a result of the inability to assign a FC adapter to a vm?
If that was the case is there any reason you couldn't run it on a VM if you are using ISCSI for lun access?
It seems to me you could use a software initiator and assign a vnic to the vswitch the ESX host uses for ISCSI access to luns.
Does VCB detect if it is being installed on a vm and not allow it?
We were able to setup VCB in the manner you are describing without any issues at all. We haven't started backing up using VCB yet but it is installed on a VM with the iSCSI initiator providing access to the LUN.
I am sure you are aware of this, but one of the main points of VCB is to offload that processing from your ESX server, and to have direct IO from the SAN. If you install it in a VM (even if technically possible) your ESX host will still be doing all the work.
Now, of course, for testing and learning this could be a great set-up!
Setting up the VCB Proxy as a VM was right in line with our goals of limiting the amount of physical servers in our remote office as much as possible. At this point we have not noticed a major performance hit on the ESX server but that could change as we had more VM's.