Hi John, hi Randall,
When I said "And it is not possible that more than 1 job writes to the same tape.", it was about that tapes still are serial access, not about interleaving.
And about the "Prefer Mounted Volumes = no" option, it is important to have it configured if you want bacula to use volumes in the same pool in the two drives at the same time.
Sorry about misunderstoods.
Regards,
Ana