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Date:      Mon, 14 Sep 1998 17:29:30 -0500 (CDT)
From:      Joel Ray Holveck <joelh@gnu.org>
To:        Terry Lambert <tlambert@primenet.com>
Cc:        joelh@gnu.org, tlambert@primenet.com, tom@uniserve.com, gpalmer@FreeBSD.ORG, irc@cooltime.simplenet.com, freebsd-current@FreeBSD.ORG
Subject:   Re: Download of FreeBSD 3.0-SNAP
Message-ID:  <199809142229.RAA09230@detlev.UUCP>
In-Reply-To: <199809141811.LAA18415@usr05.primenet.com>
References:   <199809141811.LAA18415@usr05.primenet.com>

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> Note that David points out that FreeBSD *does* do elevator sorting;
> it's still not optimal, however, since physical and logical cylinder
> boundaries are infrequently the same on modern hardware.  I have to
> look before I say any more (since I thought the code was removed
> circa 2.2.1).  David says it's called on all "dumb" drivers (wd,
> etc.); I'm not sure the "Ultra" DMA EIDE drivers are still in this
> category.

I would guess (and this is a guess, feel free to correct) that it's
still fairly good, if it simply is performing an elevator sort keyed
on block numbers.  I would expect that most translations leave the
order of the blocks alone.  (ie, if block n is closer to the spindle
than n+1, then both are closer than n+2, assuming a spiral instead of
an actual CHS.  Latency is still an issue, but not much.)  This would
mean that such a sort would still be 100% valid.

Best,
joelh

-- 
Joel Ray Holveck - joelh@gnu.org - http://www.wp.com/piquan
   Fourth law of programming:
   Anything that can go wrong wi
sendmail: segmentation violation - core dumped

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