[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 11:08:20 -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.

Supplying the missing footnote:

> 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.

[1] When I say 'the' SCSI chain, this assumes a host-bus adapter that 
provides only one chain.  However, there are also some HBAs that furnish
two separate SCSI chains.  The Linux kernel will find both of those
chains and assign them device names SCSI0 and SCSI1, in such cases.
Example:  Adaptec AHA-3940UW, described as a 'dual-channel' SCSI card.

Such an HBA is for all intents and purposes two HBAs coinhabiting a
single card.  Therefore, all remarks about SCSI termination apply to
_each_ chain.  Chain 0 must be terminated at both end devices and not at
any interior device on that chain.  Chain 1 must be terminated at both
end devices and not at any interior device on that chain.

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