Having recently had an issue which culminated in reduced responsiveness due to fragmentation of files, I have been introduced to the delights of Defraggler. There appears, IMO, to be a missing feature of this particular product which is evident in common file systems under Linux: positioning files on the hard drive with room to grow. Is there a defragmentation tool on the market which is able to perform such positioning? (For the casual reader: various file systems under Linux such as ext2 are purportedly "fragmentation-free" - this is untrue. Such file systems have mechanisms in place to endeavour to avoid fragmentation but they are not immune.)
Example: the Exchange DB on the server I experienced trouble with is some 20GB in size (made up of two files). The disc has 50% free space (after some clean up) but Defraggler still defragmented these files into early portions of the HD and then fitted other files immediately afterwards. One day afterwards these files are now fragmented significantly at their ends. Running Defraggler on these files (only), Defraggler moves the files after most other files... The following day (two days after original defrag), one of the files has become fragmented again - into the space left behind by the previous day's defrag.... Defragging this file puts the entirety of the file into the rest of the space (defragmented, obviously).
There just seems to be some missing logic: dump the biggest of files into available spaces with room to grow... (granted, file system drivers are also at fault).