Q: How do I get BRU working with my Exabyte 8700?
A: BRU has never really worked that well under Red Hat. The most common problem (halting with "bru: [E134] internal error 100 - failed self consistency and portability checks" errors) can be solved by setting the time zone varible. For example, "export TZ=PDT".
/dev/st0 and /dev/nst0 are the right devices for SCSI tape drives (unless you have more than one).
To test a tape drive, I'd do the following:
tar -czpf /dev/st0 ~
tar -xzpf /dev/st0