The lengths of the cables in the spec.s are based on other spec.s that
define among other things how the cable is built.  The spec.s are designed
to have some slop for various unknown issues of implementation and generally
are good guides.  The spec.s are based on single cable lengths, not cables
joined with couplers (this is a bad thing unless you know the spec. that
defines loss/impedance of the 2 connections you made per coupler, [this is
significant]).  You can successfully increase these lengths by purchasing
cables that are designed with increased shielding but this makes it your
responsibility to verify functionality.  I recommend keeping a set of
"golden" cables (known good cables of the same length you use) when you can.
If you have parity errors you can switch to the "golden" cables to see if
the parity errors go away. 

-----Original Message-----
From: Bob Bakh [mailto:bbakh AT veritas DOT com]
Sent: Monday, October 16, 2000 10:10 PM
To: fx AT veritas DOT com; veritas-bu AT mailman.eng.auburn DOT edu
Subject: RE: [Veritas-bu] Parity Errors flooding /var/adm/messages on
Sola ris 2.6


Still sometimes depends on the machine, on one machine 25m will be just fine
and another running Diff 25m will be too long, all depends, but I run into
this more if the customer is trying to stretch a system into the 25m limit
and has the cables coupled in the middle.  in this case 25m is too long.

And in others 30m works just fine.  All depends.  If you see the parity and
negotiating down errors, it's always good to switch out the cable before
trouble shooting farther, unless you just forgot a terminator.

=)

Bob

-----Original Message-----
From: fx [François-Xavier Peretmere] [mailto:fx AT veritas DOT com]
Sent: Monday, October 16, 2000 3:17 PM
To: veritas-bu AT mailman.eng.auburn DOT edu
Subject: Re: [Veritas-bu] Parity Errors flooding /var/adm/messages on
Solaris 2.6


> From: Bob Bakh [mailto:bbakh AT veritas DOT com]
> Sent: Friday 06 October, 2000 19:56

> One more cause which is funny, is if you use a SCSI cable
> that is just too long, what is too long, well that's up to the
> computer to decide.

 hum? and what about the SCSI specifications:

SCSI1 / Single-Ended: 6 meters.
SCSI1 / Differential: 25 meters.
Fast SCSI / Single-ended: 3 meters.
Fast SCSI / Differential: 25 meters.

 (from the SSI faq: http://www.scsifaq.org/scsifaq.html)

 fx

#include <std_disclaimer.h>

--
      fx AT veritas DOT com      | With searching comes loss
François-Xavier Peretmere | And the presence of absence;
 http://www.veritas.com/  | "My Novel" not found.

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