[Simh] VAX 8200

[Ethan Dicks]

On Fri, Mar 17, 2017 at 4:16 PM, Rich Alderson
<simh at alderson.users.panix.com> wrote:
>> From: Ethan Dicks <ethan.dicks at gmail.com>
>> 2400' tapes (1.5mil thickness) were standard but sometime later, thinner (1.0
>> mil?) 3600' tapes came out.

> At LOTS (the Stanford academic computing facility where I worked from 1984-91),
> we did nightly incrementals and weekly full backups...
>
> On the -20s, weekly backups took up 3 2400' reels (only a small portion of the
> 3rd reel being used).  When Memorex came out with their 3600' tapes, I switched
> us over to using them so that weekly backups (rotated on a monthly basis) took
> up less space; nightly incrementals used 2400' because it was almost unheard of
> fot need more than 1, and they were a sunk cost.

Nice save there.  I managed our wall of tape.  I would definitely
loved to have removed 20%-30%...

> The 3600' tapes worked very nicely on TU78/TU79 drives and on the STC drives on
> the SC-30M, and I don't recall any complaints about them on the TU81s attached
> to the VAXen.  As operations manager, I would have heard.

We had a TU78 as our big, main tape drive.  It was really fiddly about
autoload and we had DEC FS out a *lot* when it was under contract.
After we couldn't afford to keep them and all the maintenance fell on
me, I did what I could with it, and we did use it a lot, but there
were some tapes that just would not play nice.  We cleaned the glass
and did all the things.  Some tapes always worked.  Some worked most
of the time.  A few just would not autoload.  Once we could get a tape
loaded and on BOT, the drive was fantastic.   I never had enough data
about brands, etc., to figure out the loading problem.

Our TU80 was fine with whatever we put into it.  I never had a single
problem with the one from the office except after a year or so outside
the data center (at my house), the vacuum pump became unhappy, due to,
I think, high humidity in my non-air-conditioned house.

The TS03 was a beast that shredded tapes if you did not do exactly the
right things.  I didn't use it much but a couple of our folks spent a
lot of time swearing at it.

>>  I have read tape drive instructions that say not
>> to use those tapes in this machine.  I wouldn't be surprised if most DEC tape
>> drives didn't like thinner tape.

I _think_ the warning I recently read about 1mil tapes was in the
manuals for a front-loader HP 7879 drive that I was working on last
year (it passes most of its tests but is still a little cranky).

Your experience with thin tapes is vastly greater than mine.  Good to
confirm DEC tape drives are solid.

-ethan

P.S. - that TU78 was one of the 4-5 items I could not save when the
company folded.