[conspire] (forw) Re: June 25 MP installfest upgrade RH 7.3 PC to Centos56 continuation

[Rick Moen]

----- Forwarded message from Rick Moen <rick at linuxmafia.com> -----

Date: Tue, 5 Jul 2011 10:59:36 -0700
From: Rick Moen <rick at linuxmafia.com>
To: wood eddie <ewood111 at yahoo.com>
Subject: Re: June 25 MP installfest upgrade RH 7.3 PC to Centos56
	continuation
Organization: If you lived here, you'd be $HOME already.

I wrote:

> The underlying problem might be something that will be obvious to me
> when I examine your system.  Alternatively (though I think this
> unlikely), it's possible that the AHA-2940 you bought is defective, or
> is set up with grossly incorrect SCSI termination, or is badly
> misconfigured.  I cannot say until I have examined your system.

On reflection, I would strongly urge that you take the time to make sure 
that -- in particular -- you have SCSI termination set up correctly.
And SCSI IDs.

The key thing to know about SCSI termination, and the thing that novices
consistently get wrong, is that termination must be enabled at both
extreme ends of each SCSI chain, and must NOT be enabled anywhere 
interior to the SCSI chain.  Towards that end, examine the hardware
configuration of _each_ device on the[1] SCSI chain:  If you have two
SCSI hard drives and an Adaptec SCSI HBA card, that means you should
examine the hardware configuration of _three_ SCSI devices.  The device
on each end of the chain must supply SCSI termination power.  The device
in the middle of the SCSI chain must _not_ supply SCSI termination power.


Termination is, of course, not the only way to sabotage a SCSI chain
through misconfiguration, but it's the most common by far.  _Also_, and
this is equally important, you must verify that each device on the chain
has its own unique SCSI ID.  E.g.:

SCSI ID 0:  primary boot hard drive
SCSI ID 1:  second hard drive
SCSI ID 7:  Adaptec AHA-2940

It would be very bad, for example, if the Adaptec were also configured
or jumpered to use SCSI ID 0 or 1, stepping on one of the hard drives.

To those of us who've been managing SCSI hardware for 30 years, it's
easy to forget that the above isn't intuitively obvious to the rest of
the world, and that newcomers might expect hardware to automagically
configure itself, and be disappointed.


----- End forwarded message -----