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Date: Wed, 5 Dec 2001 21:06:04 +0100 (CET)
From: Roy Sigurd Karlsbakk <roy@karlsbakk.net>
To: James Stevenson <mail-lists@stev.org>
cc: Marcelo Tosatti <marcelo@conectiva.com.br>, <linux-kernel@vger.kernel.org>
Subject: Re: /proc/sys/vm/(max|min)-readahead effect????
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> thats still does not mean they are sequential creating
> large files almost always causes them to fragment.

ok...
mkfs /dev/hdb1
dd if=/dev/zero of=some-file bs=x count=x

		What can fragment this file????


after that - wget http://localhost/some-file - watch vmstat, and find it's
pushing data at around 28 MB/s

then - start ten wget's retrieving different files, and watch vmstat,
finding the maximum thoughput I can get is ~ 10 MB/s - almost one third.

If I could tell the kernel, the app (tux) or whatever, to do readahead -
say some 4 megs per file, it'd work like hell! Seeks are reduced to a
minimum and everyone's happy again

> Actually does anyone know of an easy way to find out
> if certin files are fragmented and by how much ?

I beleive there used to be a utility called 'frag' or something, to check
the fragmentation of files

roy
--
Roy Sigurd Karlsbakk, MCSE, MCNE, CLS, LCA

Computers are like air conditioners.
They stop working when you open Windows.

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