From owner-freebsd-stable  Tue Sep 25 13:49:31 2001
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Date: Wed, 26 Sep 2001 06:49:14 +1000
From: Peter Jeremy <peter.jeremy@alcatel.com.au>
Subject: Re: hw.ata.wc && hw.ata.tags && softupdates short question
In-reply-to: <20010920222727.E78811@leviathan.inethouston.net>; from
 dwcjr@inethouston.net on Thu, Sep 20, 2001 at 10:27:27PM -0500
To: "David W. Chapman Jr." <dwcjr@inethouston.net>
Cc: freebsd-stable@FreeBSD.ORG
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On Thu, Sep 20, 2001 at 10:27:27PM -0500, David W. Chapman Jr. wrote:
>I'm just speculating, but on my drive with 2mb cache, that can 
>sustain 20-30mb/sec writting, that's a tenth of a second.

Assuming that the cache contains 2MB of sequential data...

A more likely scenario is that the cache contains 100-200 chunks
of data scattered all over the disk.  100 seek/latency cycles will
stretch that 0.1 sec to more like a second and seeks are very
energy-intensive.

Peter

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