Next goes our homemade test of defragmentation speed. We created a very defragmented file system on a 32GB partition of a hard disk by loading it with music, video, games and applications. Then we saved a per-sector copy of the disk and now copy it to the HDD we want to test. The tested HDD is connected to the mainboard’s SATA controller whose operation mode (AHCI/Standard SATA) is controlled from the mainboard’s BIOS. Next we run a script that evokes the console version of the Perfect Disk 8.0 defragmenter and marks the time of the beginning and end of the defragmentation process. Thus, each drive is tested twice – with AHCI support turned on and off on the controller. You can refer to this article for details about this test.
The Western Digital RE4-GP wins this test, but by a very narrow margin. Its higher recording density and quick heads seem to do the trick. On the losing side there are two drives from Seagate (the Barracuda LP is depressingly poor) and the WD Caviar Green which seems to have problems with AHCI support.