I wrote a small script to collect the snmp data from the Brocade fibre
switches and put the data into Servergraph.
Next I created a report to graph the data and in that way we could see
historical data throughput and identified more than once a faulty tape
drive!
You definitely want to monitor your tape throughput!

> For fiber-attached tape drives - use snmp to monitor the fiber switch
ports.
>
> I use mrtg to acquire the data from my two tape-oriented SAN switches;
this feeds my hobbit (renaming, currently, to xymon) monitoring package. I
get > to see the activity for each tape drive (one per switch port) and for
each TSM HBA (one per switch port - zoned to all tape drives, run as one
primary and > 4 alternates per switch).

Marcel