UDA50/RA81 problems....

[eric at milo.UUCP]

	I would like to thank dave for clearing up a mystery
that has plagued me for some time. We have three 11/780s, all with
RA81s. After 6 months with no problems, one of them decided to go
berserk, occasionally going offline, etc. The other two continued
to perform flawlessly. Sounds like hardware, right? DEC replaced all
the controller boards, all the drives, the memory, and most of the cpu,
with no success. Finally, we installed a different driver, which
ostensibly only allowed support for ra60s, no mention of change to
how the drive was handled. Lo and behold, the problem went away.
(I should mention that the first driver was apparently acquired from within
DEC, the second, correct, one came over the net. Just goes to show who
you should trust). Anyway, I went back and checked, and sure enough, the
second driver does not issue the Get_Unit_Status command. Now, there are
still some un-answered questions, such as why that particular machine
started having problems, since it is not the most heavily loaded system,
and we tried swapping things all over the two unibuses to try and minimize
the possibility of unibus contention being the problem. Also, once the
problem started appearing, it got to the point where the system would fail
with only a few people on, mostly idle. Anyway, thanks again for clearing
up why the problem go fixed.

	On a side note, I would like to mention that the local DEC people
knew next to nothing about the drive and MSCP in general (in fact, I have
all of the "official" documentation that DEC gives them - it is hand written
explanations of some of the more common error codes), but to be fair, DEC
did fly in an expert to meet with us who was knowledgable about the drive.
He also was not able to isolate the problem, but it does seem to be a subtle
one. Anyone know if Ultrix has a correct driver?

-- 
					eric
					...!seismo!umcp-cs!aplvax!eric