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Mac OS X 10.3 Defrags Automatically
EverLurking writes "There is a very interesting discussion over at Ars' Mac Forum about how Mac OS X 10.3 has implemented an on-the-fly defragmentation scheme for files on the hard drive. Apparently it uses a method known as 'Hot-File-Adaptive-Clustering' to consolidate fragmented files that are under 20 MB in size as they are accessed. Source code from the Davwin 7.0 Kernel is cited as proof that this is happening."
"Drives are defragged to allow the OS to access the files faster."
Are you so sure?
I have talked with a senior OS designer (one of the non-free ones) and his view is that these days, defragging does more damage than it saves.
Why? Drives generally have large caches on them and multiple platters / read heads.
Noting this, the fastest way to get data off a drive might not be a straight line. Its looks pretty when you run the different utilities and makes the home makers of whom believe everything should be put away neat and tidy, but the engineer had mentioned that being defragged means you loose a lot of advantages of those multiple readheads and cache. He claimed that it was actually better to leave your drive to its own devices, allowing for about 30% free space at all times, and you will see a speedup over a defragged drive.
I didn't believe it at first, but his arguments did make a lot of sense even though it went against everything I had learned before. He actually mentioned if he had his choice, he'd make certain defraggers would NEVER work, but the market believes that these are necessary so its easier to have these things included as well as supporting third parties, so its there.