tape backup

Hi,
I have recently configured a windows 2000 server for running tape backup. It’s a dell power vault 110 using the dlt tapes. I’ve also installed veritas backup exec 8.0 on it. Everthing seems to be going ok but the only problem I’m having is thatbackup rate. It’s backing up at about 5-6 mb/min. Now this is really slow considering it takes about 9 hrs just to backup only 3 gb. We have another setup that’s on an NT machine and that one is backing up at 65 mb/min. Can someone tell me where to go to configure the backup speed?