File Sytem Backup

I have 700000 files (220 GB)on a file server. It takes over 10 hours to back this data up to a tape drive. How can reduce this time. My tape drive and file servers are on the same network switch; its a GB link between the file server and tape drive and tape speed is the not the limiting factor… I see a lot of disk I/O during backup. I think defragmentation before backup may help. What else?