Linux+RAID+backup?

["J. E." <jae CMA MGH Harvard EDU>]

Hello everyone,
 
What suggestions do you have for backing up RAID disks attached on 
a PC running Linux?
 
Our network mainly consists of Sun workstations that are currently being
backed up using an Exabyte 8mm tape drive.  We are using dump (SunOS 
filesystems) & ufsdump (Solaris filesystems).
 
We attempted to backup the RAID attached on the newly purchased 
Linux box, over the network to our Sun backup server, but the 
throughput was very slow.  We are now thinking of purchasing 
a new tape drive and directly attach it to the Linux box.  
 
* Has anyone done this?
* I would appreciate suggestions on how to backup our new RAID disk.
 
Specifications:
   Intel Celeron (Gateway) RedHat Linux 2.2.5-15
   Arena IDERAID5-84 with 32bit PCI Ultra-Wide SCSI
   (will we have to get another SCSI card to attach an 8mm Exabyte
    tape drive to the PC?)
 
Thanks in advace for your help.
Please let me know if you need more information.