Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!bloom-beacon!apple!dwells
From: dwells@Apple.COM (Dave Wells)
Newsgroups: comp.unix.aux
Subject: Re: mkfs interleave factors
Message-ID: <32029@apple.Apple.COM>
Date: 31 May 89 01:27:19 GMT
References: <31426@apple.Apple.COM> <31611@apple.Apple.COM> <182@farbmac.UUCP>
Distribution: usa
Organization: Apple Computer Inc, Cupertino, CA
Lines: 40

In article <182@farbmac.UUCP> goldfarb@farbmac.UUCP (Benjamin I. Goldfarb) writes:
>In article <31611@apple.Apple.COM>, dwells@Apple.COM (Dave Wells) writes:
>> Our own HD 20 SC performs best at 2:1 with a mkfs gap of 1.  Format it with
>> a 1:1 interleave and you'll nearly halve the performance.  Ouch.  Of course,
>> our HD SC setup program almost forces a 1:1 interleave when 'initializing'
>> on a MacII series.  You have to go through the cmd-I trick to use anything
>> else.
>> 
>> Yep, customers have asked me for the optimal settings for this drive and
>> A/UX.  I spent plenty of time playing around with whatever drives I could
>> dig up - That's how I came up with 2:1 for this one.  Other low-performance
>> drives will create the same problem when a 1:1 interleave is used.
>
>I have a Quantum Q280 internal 80 meg drive and a Quantum P80S external 80
>meg drive.  I've formatted them both with 1:1 interleave and I use mkfs gap
>of 1.  On one of the disks (the external), I have a 60 Meg MacOS partition
>in addition to A/UX data.
>Here's the question: if I accept Dave's advice and reformat both drives 
>with 2:1 interleave, will I decrease performance when using MacOS?  I assume
>the answer is yes or Apple wouldn't recommend 1:1 interleave for Mac IIs.
>If that is the case, is what I have now a reasonable compromise?  Or would
>it be better to leave the outboard drive as is and just reformat the internal?

Both of the Quantum drives you have should perform best with a 1:1 interleave
as I think they both have at least partial track buffering.  When I recommended
2:1 for the interleave, I meant only for drives without this buffering.  If you
reformatted your drives with 2:1 Mac OS and A/UX performance would suffer.

You're right about drive configuration being somewhat of a black art.  And I
agree with you.  It probably won't get much better anytime soon.

-Dave

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           Dave Wells, Apple Computer, Inc.  MS: 37-O  (408) 974-5515
          Mail: dwells@apple.com or AppleLink d.wells or GEnie D.WELLS
 These opinions may be nothing more than the ramblings of a fatigued tinkerer
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 There's one big difference between genius and stupidity.  Genius has limits.
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