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Date:      Mon, 11 Nov 1996 17:45:17 -0600 (CST)
From:      Karl Denninger  <karl@Mcs.Net>
To:        gibbs@freefall.freebsd.org (Justin T. Gibbs)
Cc:        andreas@klemm.gtn.com, acorreia@marlin.com.br, hackers@freebsd.org
Subject:   Re: Problems restoring Backups !!!
Message-ID:  <199611112345.RAA10212@Jupiter.Mcs.Net>
In-Reply-To: <199611112303.PAA17972@freefall.freebsd.org> from "Justin T. Gibbs" at Nov 11, 96 03:03:09 pm

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> 
> >options		AHC_SCBPAGING_ENABLE
> >options		AHC_TAGENABLE		# still makes problems with tap
> >es
> >options		SCSI_REPORT_GEOMETRY
> >
> >I get now thousands of (looping) Queue Full lines, when trying to make
> >a backup using dump(8).
> 
> Remove the printf and see if it works okay for you.  The printf probably
> causes a cascade effect since it will cause syslogd to write to the disk.
> I'll also look into changing the code to try to actively reduce the number
> of transactions allowed to the target, but to do that correctly is a lot of
> work - which is the main reason I added it to the generic SCSI layer on the
> SCSI branch.

Where can I find documentation on those AHC_* options, what they do, what
they might break, and when (or if) I should enable them?

My problem with turning them on is that I've heard that some older disks
puke badly with them enabled.

On the other hand, I presume there are *serious* performance enhancements
available with them, specifically tagged-queueing.

On our news server systems, I bet we could use that.  But if its going to be
something that comes at the risk of data corruption I'm leaving it off!

--
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