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From: agm@daphne.stl.stc.co.uk (Andrew G. Minter)
Newsgroups: comp.os.minix
Subject: Re:  fdisk, head, cylinders and blocks
Message-ID: <4463@stl.stc.co.uk>
Date: 23 May 91 08:54:38 GMT
References: <53806@nigel.ee.udel.edu> <1991May22.050418.189@skypod.guild.org>
Sender: news@stl.stc.co.uk
Reply-To: agm@daphne.stl.stc.co.uk (Andrew G. Minter)
Organization: BNR Europe Ltd., Harlow, Essex, England
Lines: 28

In article <1991May22.050418.189@skypod.guild.org>,
marc@skypod.guild.org (Marc Fournier) writes:
|> 	If anyone ever has this trouble again, don't go looking through
|> atwini or xtwini, you will be wasting your time..there isn't anything in
|> there.

There are however some implicit assumtions about disk geometry in the
FS.  It's in read.c if I remember correctly and it's to do with doing
read-ahead.  Minix is supposed to read ahead the rest of the track
following a read to increase speed.  The trouble is, if the FS has a
totally wrong idea about your geometry this can actually slow the file
system down.  Another problem here is that IDE drives often lie about
their real geometry and pretend to have a different layout.  They also
tend to do track buffering in hardware.

My inclination is to totally disable the read-ahead stuff.

NOTE: This problem will *not* break anything, it's just a performance issue.

Andrew
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