mkfs interleave factors

[Dave Wells]

In article <31426 at apple.Apple.COM> rick at apple.com (Rick Auricchio) writes:
>Just a quick note on what to use for the mkfs parameters for "gap" and
>"blocks/cyl".  Use 1 and 1.
>
>My tests have verified the observation that things are markedly slowed down
>by the bogus defaults of 7 and 400.  I'm now changing those defaults to 1 and 1
>for a future (post-1.1) release.
>
>Use of 1 & 1 works fine on the drives I have here; Quantums have partial and
>full-track buffering, hence they work well at 1-1 interleave.  Seagates don't
>have onboard buffering, but A/UX 1.1 makes the 1-1 physical interleave anyway
>with the Vulcan I/O acceleration code.

Hello Rick,

I got your link and saw your posting on the subject.  Just thought I'd add
my 2 cents.

It's also important to remember about physical interleave when preparing a
drive for A/UX.  Most drives (any I can think of) that provide even partial
track buffering will work great at a 1:1 interleave.  Unfortunately, not all
do provide this buffering.

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.

-Dave

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           Dave Wells, Apple Computer, Inc.  MS: 37-O  (408) 974-5515
          Mail: dwells at 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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