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Newsgroups: comp.os.386bsd.questions
Path: sserve!newshost.anu.edu.au!munnari.oz.au!spool.mu.edu!agate!tfs.com!julian
From: julian@tfs.com (Julian Elischer)
Subject: Re: Disapearing Disks?
Message-ID: <CvHGot.B7x@tfs.com>
Organization: TRW Financial Systems, Oakland, CA
References: <341uf9$d4@shore.shore.net>
Date: Fri, 2 Sep 1994 03:36:29 GMT
Lines: 50
In article <341uf9$d4@shore.shore.net>, Robert Withrow <witr@rwwa.com> wrote:
>FreeBSD 1.1.5.1, AHA1542, three Maxtor LXT312S drives, one Sony CDU541,
>one Viper 2150S tape.
>
>Recently I have been experencing a situation where, after the system
>has been running for a while one or more if the disks will cease to
>be available and I get a ``Unit Attention'' on them, and they become
>de-configured. Note: by ``running for a while'' I mean running for
>a while after being re-booted. The system is *never* turned off for
>more than a few seconds, so the problem doesn't seem to be heat
>related. I have blown out the dust every now and then. I have
>carefully configured the scsi bus so that <5 targets are supplying
>terminator power. The cable is custom, since no one makes a scsi cable
>with 5 connectors.
I would suspect your power supply.
The "Unit Attention" is produced by the DRIVE and not by the driver
(though it relays it to you). This usually means that a removable pack
has been changed, or that the drive has been off-line for some reason
and has come back on.. In my experience this is usually because
something caused them to start their 'power-fail' sequence.
A "unit attention" message usually means that teh mounted media might not
be trustable. As the driver also supports removable media, it immediatly
dissallows all further access to the drive, until ALL open sessions
have closed, and then re-allows new 'open' calls. This is because it has
reason to believe that media has been changed and that continuing a
mount session over a media change might be a bad idea. It has occured to
me that I might have made this action dependent on whether the
device reported in as "removable", but that doesn't cover the case
where someone turns off a drive and unpluds it, and substitues a differnt
one.. (The new drive should respond with "unit attention" to the first
command sent to it).
Anyhow, your symptoms sound like a power supply problem..
(are they on the same power supply, same power point, sharing a circuit
with the microwave?) :)
particularly as you mention that several drives can be affected
at teh same time. (unless something puts out a "Bus RESET" on the scsi bus
but the they'd ALL go off line).
personally I'd only allow termination power from ONE device (the end one)
not 5
julian
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