I don't think I'll be able to help you much, but I can give you a few
pointers on where you can get more help.  I had raised a similar question
in September, 2000, and so if you were to go to
http://mail-index.netbsd.org/ (which is where all the netbsd mailing lists
are archived), and go to the netbsd-users and netbsd-help list for that
month, you just might find some info.

Infact,  I went thru those mail myself just now, and have fished a link I
found to a tut posted by somebody (Mike Pelley) --
http://worldmap.net/raid.html.  It might help.

[Basically, I never got abt to using RAID (coz I had 2-3 OSes on the same
machine, and that was a problem) and so would not be able to help much.]

Hope this helps.

Regards,
Rakhesh