OS X defrags files smaller than 20MB on the fly. Files larger than that do not normally suffer significant performance penalties given the sizes of disk buffers on current hard drives. Defragging will actually hurt as well. OS X keeps track of your most often used files and moves them to the "Hot Zone" for an extra performance boost. So messing the Hot Zone up will only slow things down.
If you require high performance audio/video disk access then you probably want to start your projects on independent and clean partitions anyway, so defrag doesn't even help there.
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OS X defrags files smaller than 20MB on the fly. Files larger than that do not normally suffer significant performance penalties given the sizes of disk buffers on current hard drives. Defragging will actually hurt as well. OS X keeps track of your most often used files and moves them to the "Hot Zone" for an extra performance boost. So messing the Hot Zone up will only slow things down.
If you require high performance audio/video disk access then you probably want to start your projects on independent and clean partitions anyway, so defrag doesn't even help there.
more on HFS+ defrag