There is really no good documentation about SCSI tape backups on the web -
I know, since I went through setting up my own recently. 

I really don't know enough about them to set up a LDP "howto" on SCSI
tape drives, but I may give it a shot anyway - just to get _something_ out
there. 

Your tape drive should show up as /dev/st0

To back up your system to the tape drive with tar, 

cd /
tar cvMf /dev/st0 *

There are probably lots of options you should add to that basic syntax, to
prevent backing up the /proc directory, and/or any CD-ROM drives you may
have mounted, etc...  I'm sure someone else would be able to elaborate the
tar command (and/or CPIO) - since tar is used for nearly everything (not
just SCSI tape backups)

When the SCSI driver loads (via module or directly in the kernel), it
should display a summary of devices on each SCSI id - including your tape
drive. 

If your tape drive has an auto-changer, you may have to enable probing
SCSI LUNs in the hardware configuration for the auto-changer to be
detected.