Adding a 3rd party SCSI disk to an rs6000

[John P. Eisenmenger]

I'm trying to figure out how to set up a WREN-VII for my RS6000.  Has
anyone done this before?  The problem, as I see it, is that I need to
define a new disk subclass in order to get little things like the disk's
size correct.  How do I go about it?

I'm also having some troubles with a SCSI 8mm tape drive.  It looks
like its configured (marked as available, correct subclass, and device
files are there), but whenever I try to access it I get:

  /dev/rmt1: A system call received a parameter that is not valid.

Help in any form (mail, follow-up articles) will be digested and
appreciated.

-John