Our VMs are on a SAN with faster SSD drives. This SAN will strictly be fore backups.
Just so I am understanding correctly the process would be....
Create a volume on the SAN
Rescan the storage adapters from Vsphere
Add a new datastore using the new volume
Add a new drive on the Veeam VM that connects to the new datastore
Send backups to that drive.
create a host object for the Software iSCSI Initiator from the B&R Server VM on your backup target storage.
Allow this host object to see the volume (create a LUN).
Go to the B&R Server iSCSI Initiator and add the Storage and Volume to windows.
Format the volume with ReFS 64k.
You do not need to create a datastore, since it is a target storage. Present the volume to Veeam B&R, as Andreas has mentioned, and format it with ReFS within Veeam B&R server operating system (not within vSphere).