This is a very hot topic on the net lately. A user on his own website posted how
to defrag on Linux which is not easy to do. His starting point was that it is a
mistake to believe that Linux drives do not get fragmented. Then he got a lot of
people saying that it was unnecessary and flaming him for even suggesting it.


While it is a contentious subject to be sure, most people agree that you do not
need to worry about it provided you don't let your drive get over 80% full.
After this large files can become fragmented as the file system has no
alternative than to put the file in available spots, breaking them as necessary.
However, if you delete some files the file system will in the background move
the large files and defragment the drive in the process.

The big difference is that Linux files systems are journaled (ext 3 and Reiser)
and it spreads files across the drive, leaving space for the file to grow as it
does this. Journaling is a way of keeping track of the file system and changes
made. If the system crashes the journal helps to protect from truncated files as
all changes are saved to a log.