From Wikipedia, the Lunixfag basher:
Defragmentation
There is no online ext3 defragmentation tool working on the filesystem level. An offline ext2 defragmenter, e2defrag, exists but requires that the ext3 filesystem be converted back to ext2 first. But depending on the feature bits turned on the filesystem, e2defrag may destroy data; it does not know how to treat many of the newer ext3 features.
There are userspace defragmentation tools like Shake and defrag, which work by copying each file and hoping the newly allocated file was not fragmented. However this only works if the filesystem is reasonably empty, and such filesystems are not usually fragmented. A true defragmentation tool does not exist for ext3.
Also
>>4? Defragmentation is an essential part of hard drive storing.