Access fibre-channel tape library through RMAL?

The key advice for "do not virtualize the media server" relates to hardware access of storage devices used as backup targets. We do not test or certify any passthrough technology as a target device connection. - This means SCSI, FC, SAS, USB connected drives (tape or disk) that are passed through may experience unpredictable timeouts etc that cause problems.

Storage inside a vmdk held in a datastore and (in theory) iSCSI storage should be OK.

If doing VMware backups you cannot use SAN transport mode inside a VM (not supported by VMware) however HotAdd Transport actually requires the media server to be a VM (which is probably the only reason to virtualize your media server)

Also if running deduplication because the overheards can be large against disk read/write performance, CPU and Memory requirements it is also recommended that physical harwdare is used so that the resources are not affected by sharing with other (virtual) servers.