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From: jar@ifi.uio.no (Jo Are Rosland)
Newsgroups: comp.unix.admin,comp.unix.questions,sussex.general,comp.misc
Subject: Re: Disc (De)Fragger
Message-ID: <JAR.91May11211108@gyda.ifi.uio.no>
Date: 11 May 91 19:11:17 GMT
References: <4973@syma.sussex.ac.uk> <1991May01.154043.1031@scuzzy.in-berlin.de>
	<1991May2.024639.9011@maverick.ksu.ksu.edu>
Sender: jar@ifi.uio.no (Jo Are Rosland)
Organization: University of Oslo, Norway
Lines: 23
In-Reply-To: brtmac@maverick.ksu.ksu.edu's message of 2 May 91 02: 46:39 GMT

In article <1991May2.024639.9011@maverick.ksu.ksu.edu> brtmac@maverick.ksu.ksu.edu (Brett McCoy) writes:

   One reason such a tool doesn't exist for BSD 4.2 filesystems is that
   it is built in to the filesystem.  The 4.2 filesystem does it's best
   to keep a disk from fraging, and to unfrag a disk that is fragmented
   as files are read and then rewritten.  The 10% diskspace buffer that
   is suggested for filesystems is to allow the extra space with which
   to perform this task.  If you cut the buffer down to 0% and then fill
   the disk up it will fragment rather badly, but so long as you leave
   the 10% free space you will usually never get more than 3-4%.  On
   my news partition the worst I have ever seen it get is 4% after months
   of use.

When you talk about fragmentation percentages here, do you mean the
output from fsch when booting?  Well, that's not a measure of
fragmentation as the original poster meant it.  The thing is, under
4.2BSD file systems, you've got something called "fragment blocks",
and the "frags" percentage from fsck is just the percentage of data
blocks that are used as fragment blocks.  It's not a measure of
fragmentation at all.
--
Jo Are Rosland
jar@ifi.uio.no