why no defragmentation in linux
 

So I read on the Internet that it is not necessary to defragment a Linux system. I have been using windows now for a while and the whole idea of fragmentation makes plenty of sense to me. What doesn't make sense is how the file systems on linux get by without this. In Windows if you don't defragment every week or so your computer starts to get really sluggish. Can someone point me to an article about this, I have tried searching the web (google, a9.com) but to no avail. Thanks for the help.

It isn't necessary because the file systems work in different ways. With the way FAT and NTFS works it definitely makes sense to defrag, with the way ext3 works it doesn't make a lot of sense at all.

Links:
https://listman.redhat.com/archives/.../msg00026.html
http://lists.debian.org/debian-user/.../msg03496.html
http://www.itworld.com/Comp/3380/nls_unixfrag040929/

Is true of all journaling file systems, I ask this 'cause I use reiserFS?

This has been discussed a lot on this site. Use the search function to look for similar threads and you will get lots of info from previous discussions.

Do not know the tool for reiser, but with ext2/ext3 could be used.

Defragging in windows only makes sense because people have become used to fact that overstretched floppy drive based filesystems (ie FAT) were used on ever larger hard drives they were never designed for and so need defragging... Filesystems like ext2/3, reiserfs and even ntfs were designed with larger drives in mind and don't suffer the same problems.