I know everybody says EXT3 and EXT4 filesystems don't need defragmentation and in most cases, that's true! But sometimes they actually do need defragmentation. There is an entire discussion rather or not EXT3 needs defragmentation but I'll not get into that. It just depends on the way a filesystem is used, when it was last formated and how full it is. So don't take my word for it, and go take a look at the fragmentation level (will tell you how to do that in just a moment) of your hard drive.