> Does anyone have experience with the Adaptec 2940 controller??
> 
> Everything appears to be probing and connecting fine, but when I try and write
> a tape using the Archive tape drive, it writes merrily along for awhile
> (several megabytes,) then gets an I/O error.
> 
> I've tried tar'ing with /dev/rst0 and /dev/nrst0, no difference.

don't worry if it's not that, but check termination.
 
i were searching for source of problem on one machine with effects like
yours and finally found that termination jumper is not inserted correctly