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Date:      Thu, 13 Jul 1995 11:13:20 -0500 (CDT)
From:      Karl Denninger <karl@Mcs.Net>
To:        davidg@Root.COM
Cc:        karl@Mcs.Net, freebsd-hackers@freebsd.org
Subject:   Re: SCSI disk wedge
Message-ID:  <199507131613.LAA01942@Jupiter.mcs.net>
In-Reply-To: <199507131536.IAA05001@corbin.Root.COM> from "David Greenman" at Jul 13, 95 08:36:06 am

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> 
> >Since there are no errors presented to us when the 1742 hangs, and the 
> >2742 starts complaining about timeouts, I don't know where to go next.
> >Tagged queueing is not at issue; I have tried with it both enabled and
> >disabled.  With it *ON* the incidence of the hangs is reduced, but not
> >eliminated.
> >
> >It LOOKS like something has requested an action on the SCSI bus which is
> >causing problems (ie: disconnect sequencing, etc) for devices, and/or the
> >adapter itself, causing a wedge condition.  Why this is not detectable and
> >correctable (or at least abortable with a panic) in the driver is unknown 
> >to me.  The kernel IS running -- I can telnet to the machine affected and
> >get connected, but any disk I/O attempt goes nowhere.
> >
> >There is a difference -- the 2742 is MORE stable than the 1742.  The
> >1742 machines run about 8 hours before dying -- the 2742 with MUCH 
> >heavier load on it can, in some cases, run for 2-3 days.
> 
>    I suspect that BSDI runs longer because it detects the wedge and can
> successfully unjam the bus. FreeBSD is known broken in this regard, and
> several people are working on fixing it.
> 
> -DG

If that's happening, it is happening silently.  We haven't gotten any error
messages related to SCSI issues on BSDI.

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