Instructions
Linux and Mac OS computers do not come with defragmenter utilities. That's because they handle files differently than Windows and essentially take care of file fragmentation as it happens. PlayStation 3 hard drives handle adding and removing files the same way.
PlayStation 3 handles files just like Linux, in a format called CellFS, so your game files are never fragmented in an appreciable sense, as they would be if it ran on a Windows platform.
Since there is no fragmentation, there is nothing that needs to be done to care for the hard drive.