SOLVED: External disk hangs the system

From: Michael C. Grant <mcgrant_at_wheezer.Stanford.EDU>
Date: Mon, 15 Apr 1996 05:39:30 -0700

Well, thanks to the power of the Web (and process of elimination :-) I
was able to determine the problem. I pulled apart the disk chassis to
find out that the jumper enabling termination power had been removed.

>From a couple of SCSI-faqs sprinkled throughout the Web, as well as
from the Web site for Quantum Corp., I learned that it really is
recommended that every device supply termination power to the bus.
So, I borrowed a non-critical jumper to test it out, and BINGO, it
worked. Funny how that happens.

Anyway, I also received responses from two people, whom I will thank
right now... Their text is given below.

Thanks
Michael

------
From: T.A.P. Green
Date: Mon, 15 Apr 96 13:26:44 BST

Michael,

Unfortunately, a SCSI hang can be caused by lots of things.

Namely;

   a) SCSI cable length. Its very easy to exceed, devices themselves
      use cable length, as much as one metre.

   b) Faulty SCSI controller or cable or terminator.

   c) Incompatible FIRMWARE on the disk drive or system.

   d) Something else!

In my case, it was being caused by a partitially terminated
SCSI ribbon cable inside the case of the AXP-2000.

I've got quite a good article on hunting SCSI faults, which
I will dig it up and forward to you, together which other
responses (which wern't that helful in the end but may be good
for your problem ).

In general, AlphaStations seem to have quite short maximum
SCSI cable lengths, the AXP-2000 was 1.5 metres, basically
enough for one external device.

Try out different cables and terminators first, make sure
terminators are of the ACTIVE type.

A second SCSI card may also be useful for trying out the
disk on the Alpha.

Good luck,
Tristan

----
From: Harry Eleftheriou 
Date: Mon, 15 Apr 1996 07:38:04 -0400
Michael,
I would say it is either misconfigured or has a problem internal.  Excess 
termination (like not enough) can cause intermittant problems of the most 
elusive nature.  I have seen systems with SCSI cables only 6 inches too long 
and the system can run for weeks or < hours.  It is frustrating to 
prove/disprove where the fault really is.
I would also check the console settings (if available on your Alpha) to see 
if any relevant SCSI setting may be needed for your system.
Check with the manufacturer to see if there may be a firmware issue with 
this drive.  A while ago, there were a bunch of Quantum drives which had 
problems with Alphas and Windows NT but the model number you quote does not 
trigger my memory re this particular problem I refer to.
Cheers,
Received on Mon Apr 15 1996 - 15:32:57 NZST

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