From:	MERC::"uunet!WKUVX1.BITNET!MacroMan" 29-MAY-1992 14:46:16.66
To:	MACRO32@WKUVX1.BITNET
CC:	
Subj:	Re: MTFO...

>Date sent:  29-MAY-1992 10:01:23
>
>
>        We've got a nonlocal configuration which is as follows:
>                [VAX 6430]-(cibca)--[star coupler]--(hsc70)-{RA90s}
>
>        Periodically all DECserver drop our VAX service and disconnect
>        all users.  This occurs at times of extremely high load on the
>        system.  Additionally, it has been noted that the HSC is maxed
>        out several times during the day.
>
>        Field Service:  Oh yeah, you're maxing out your HSC so you're
>                        hanging.  Buy more {xxx}
>
>        Ehud Gavron:    What should happen is that IOs should be pending
>                        and queued, not a hang for many seconds.
>
>        Data: LTDRIVER does its work at IPL 8.  PADRIVER at 20.  An
>              outage of 2.55 seconds or more would cause this problem.
>
>        I still insist it's a hardware problem; all the CI cards (VAX,HSC)
>        have been changed.  Can anyone out there tell me if they've seen
>        this before, if it was hard or soft, and what the solution (if
>        any) was?
>
>        Ehud
>
>--
>Ehud Gavron     (EG76)
>gavron@Spades.ACES.COM

        I while ago I had the same problem with DECservers dropping
users.  This was on a 6410/8530 CI cluster with an HSC70 and RA90s.  The
problem did not seem to correspond to any particular load on the system and
I know the HSC wasn't maxed.  What I did know is that I just upgraded LAT
to 5.4 the day before.  DEC admitted numerous problems with LAT 5.4
(specifically LTDRIVER) on 6000 series machines and provided me with a patch
that didn't work either.

        For some unknown political reason Babson can't afford any
down-time so I didn't have the chance to dig in and find out what was
really going on.  I assume you are running a higher version of LAT than
this, and the circumstances are different, but the problem was the same
and here it was a software problem. The fastest solution was to drop
down to a pre-LATmaster version of LAT.  (weak but it worked)

                        John

John Shea
Systems Manager
Babson College
Shea@Babson.Bitnet
(internet address soon to show here!)