you can use ufsdump with tapes (default it writes to /dev/rmt/0, which is the "first tapedrive on the system" - it does not matter if DLT or 8mm, the name is always the same) or with files (or remote files)
eg make a dump of c0t3d0s0 to local drive:
ufsdump 0f /dev/rmt/0cbn /dev/rdsk/c0t3d0s0
eg make a dump of c0t3d0s0 to a remote drive (edit ~/.rhosts for login without password!)
ufsdump 0f remotehost:/dev/rmt/0cbn /dev/rdsk/c0t3d0s0
Both DLT and 8mm is ok; I think DLT would be faster and has mor capacity per Tape!
RAID5: yes and no; I recommend to make a backup of this filesystem, too. Any activities on the rootfilesystem SOULD NOT HARM the RAID5 but do you know Murpy's Laws!?

BTW 9 Drives for RAID5 is not realy recommended (but will work of course)
Regards
-- Franz
Sorry I'm not a native spaeker, I'm from
Munich, Germany - "Home of the Whopper", oh no, "Home of the Oktoberfest" ;-)
Solaris System Manager; I used to work for Sun Microsystems Support (EMEA) for 5 years