You can try increasing the block size on your device. You can also set the logging to Log Directories
If you are in a SAN, you can zone your tape device to see thsi server, and back it up locally instead of over the LAN
Check you LAN connections and make sure that you are using Full Duplex instead of AutoNegotiate
However, I think that, in the end, you just have a slow network. and, from a Data Protector perspective, there is really not much you can do about this
I have attached a doc with various things that you can do to speed up performance
