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From: Rashid  Karimov <rashid@rk.ios.com>
Message-Id: <199606181359.JAA13394@rk.ios.com>
Subject: AHC/SCSI stability (resets/timeouts on SCSI)
To: freebsd-stable@freebsd.org
Date: Tue, 18 Jun 1996 09:59:52 -0400 (EDT)
Cc: questions@freebsd.org
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		Hi there folx,

	I've changed the topic of some other thread here
	( famous trap 12 one) to something more relevant
	to the Q I have. The cites below are from Justin's
	answer on kernel config issues.



	I run rather large CCD PC here - it has 3 AHA2940W
	and 6 HDDs in it ( it's a news server) .
	Works very fast - reads/writes at ~18MBs.

	It can ran up to a few weeks w/o any problems,
	but every once in a while I would see these messages in the
	messages file:


	Jun 11 21:49:45 news /kernel: ahc2: Issued Channel A Bus Reset #3. 0 SCBs aborted
	Jun 11 21:49:45 news /kernel: ahc2: target 1, lun 0 (sd5) timed out
	Jun 11 21:49:45 news /kernel: ahc2: Issued Channel A Bus Reset #3. 0 SCBs aborted


 /kernel: sd5(ahc2:1:0): UNIT ATTENTION asc:29,0
 un 11 21:49:49 news /kernel: sd5(ahc2:1:0):  Power on, reset, or bus device reset occurred field replaceable uni
 t: 1
 Jun 11 21:49:49 news /kernel: , retries:4
 Jun 11 21:49:49 news /kernel: biodone: buffer already done


	and machine would reboot or hang :(
	Sometime all three ahc* would complain ...

	
	The ahc driver is from 2.1-release I think. Is there anything I can
	do to make the machine more stable ? I want to give a try to ahc
	driver from latest 2.2.-SNAP to see how it goes .

 >Here is my kernel configuration:
> 
> >controller      ahc0
> >controller      ahc1
> 
> You only need one of these.  One ahc entry will attach to as many cards
> as it can find in your system.

	I have 3 entries actually - can it somehow affect stability 
	of the SCSI system ? 
	I can't go with whole new kernel though - the ccd is now made
	as LKM and is not backward compatible as I heard ? 
	Is there a chance I can use old ccd code with 2.2-0612-SNAP ? 



	
> 
> >Basically I stripped everything I didn't need in the hopes
> >of expurgating the problem.
> 
> Not quite everything.
> 
> >An issue with the 2940W?  I did have to disable wide 
> >transfers on the wide drive and sync negotiation for both (not sure 
> >which fixed it) to make the narrow drive stop rebooting the SCSI bus
> >on every drive access, but that was a dozen sups and kernels ago, 
> >haven't had time to play with it since.
> 
> Please confirm that you no longer need to disable wide negotiation or
> lower the sync rate with the latest driver.  This should be fixed.
> 
> >Later,
> >Jeff
> 
> --
> Justin T. Gibbs


	Rashid.