Re: Ext2 defragmentation

Theodore Y. Ts'o (tytso@mit.edu)
Fri, 12 Nov 1999 15:23:02 -0500


Date: Fri, 12 Nov 1999 20:33:50 +0100 (CET)
From: =?ISO-8859-1?Q?Mads_Martin_J=F8rgensen?= <mmj@mmj.dk>

How necessary is it to defragment ones ext2 partitions? It just hit
me that defragmentation is very important under the Wintendo
filesystem. I'v= e found the program e2defrag which is just a small
hack done to defrag (Stephen C. Tweedie) to make it work under the
2.2 kernel. The problem is that in the README-0.71 it says:

"I have NOT tested this yet, all I know is it compiles and *should*
work, but I am not making any gurantees, so DO NOT use this on any
filesystems with important data that you have not backed up. It would
perobably even be a good idea to test this on a dummy filesystem
first.

It's not necessary under most normal conditions, which is one of the
reasons why the e2defrag preogram hasn't really been maintained.
E2fsck displays a statistic, "number of non-contiguous files", which is
roughly a good metric for how fragmented the filesystem is, except if
you have lots of large files, since large files that are bigger than a
block group (8 megs or 32 megs) have to be non-contiguous by the nature
of the ext2 filesystem.

Under most operating conditions, defragmentation really shouldn't be
necessary.

- Ted

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