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From: "Rodney W. Grimes" <rgrimes@gndrsh.aac.dev.com>
Message-Id: <199508311754.KAA12139@gndrsh.aac.dev.com>
Subject: Re: 4GB Drives
To: gibbs@freefall.FreeBSD.org (Justin T. Gibbs)
Date: Thu, 31 Aug 1995 10:54:28 -0700 (PDT)
Cc: pete@kesa26.kesa.com, jbryant@argus.iadfw.net, freebsd-hackers@freebsd.org,
        pete@rahul.net
In-Reply-To: <199508311611.JAA11646@freefall.FreeBSD.org> from "Justin T. Gibbs" at Aug 31, 95 09:10:54 am
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> 
> >Now, can you all leave me alone for 30 days so I can go get the stripes
> >working, I have small bottleneck that needs fixed :-):-):-)  And can
> >anyone tell me what the mean and standard deviation of an I/O request to
> >an aic7870 is before it hits the drive given 0 scsi bus contention?  This
> >seems to greatly effect rotation offset on stripe sets when pushed to
> >the limits of data coming under the head just after the I/O hits the
> >drive.
> 
> Hmm.  You'd have to come up with some way to benchmark it since its very
> dependant on the sequencer code.  I'd be interested to here what your
> results were. :)

:-).  How much control do you have over the controller LED in the sequencer
code?  Would it be possible to wink it when an I/O CCB comes in from the
host, and then double wink it when it goes out the scsi bus?  Or am I
going to have to find a 128 channel logic analyzer and pull my hair out
for a week to try and capture this :-).

> So, are you planning on using a 3940W for this type of application?

Possibly, prototypes are NCR 825 and aha2940W right now...

-- 
Rod Grimes                                      rgrimes@gndrsh.aac.dev.com
Accurate Automation Company                 Reliable computers for FreeBSD