WAS: Disk upgrade problem | NOW jumper ?

[Rick Stevens]

Bob McClure Jr wrote:
> On Sun, Oct 24, 2004 at 05:14:12AM -0700, Stephen W wrote:
> 
>>Bob McClure, Jr wrote:
>>
>>
>>>BTW, _always_ use master and slave jumpering on the
>>>drives.  "Cable Select" (CS) is unreliable at best  
>>
>> > and evil at worst.
>>
>>
>>What kind of problems are there with cable select?  I
>>have been running my HD so configured and not had any
>>problems that "seem" to be so related.
> 
> 
> I've always used master and slave jumpering, so I've not experienced
> any problems with CS.  Googling for "cable select" and "evil" or
> "sucks" turns up some interesting anecdotal evidence:
> 
> http://www.redhat.com/archives/fedora-list/2003-November/msg05412.html
> http://archives.mandrakelinux.com/newbie/2002-11/msg02246.php
> 
> Or you can toss a piece of meat to Rick Stevens and he will wax
> vociferous on the subject.

Yowmmf!  Gnaw!  Gnash!  Raw meat!  Yum!

Cable select is dangerous in several respects.  First, it depends on the
electronics on the drive to handle the tri-state nature of the select
lines.  Second, all drives must handle cable select in EXACTLY the same
manner.  This includes the electrical environment, backoff timing,
waveform shape and the arbitration between the devices and was a problem
between different drive makers (e.g. Maxtor and WD wouldn't do cable
select nicely between them).

Third, the electrical environment can affect the reliability of cable
select.  If there's lots of stray signals in your machine (as is common
with older mobos), these can screw up the selection.

In general, NEVER rely on cable select.  IMHO, it was a stupid idea from
the get-go.  If you can't figure out that one drive should be jumpered
as master and the other one as slave, then you really shouldn't be
poking around inside your system in the first place.  SCSI never
supported cable select, and now you know why.  It's unreliable at best.

>>However, that may not be true.  I have not had boot
>>problems (which is what I would expect).  
>>
>>Maybe I should pull out my drives and jumper them? 
> 
> 
> Nah.  If it ain't broke ...  But at the first sign of trouble,
> particularly after changing something, I would.
> 
> 
>>Are the problems on older MD? (I am running a
>>relatively new MB: ASUS A7N8X-Deluxe.)

Make sure your mobo has the latest BIOS in it.  The rest of the
solution Bob covered pretty well in his first missive.  You'll need
to boot in recovery mode off the first CD and do a grub-install from
the chroot environment.
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- Rick Stevens, Senior Systems Engineer     rstevens at vitalstream.com -
- VitalStream, Inc.                       http://www.vitalstream.com -
-                                                                    -
-     Try to look unimportant.  The bad guys may be low on ammo.     -
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