question about defragging

You don't need to do it.

 

A little bit more specifically, the reason you do not need to defrag is because OS X defrags on the fly! It's great not to have to worry about that.

 

Actually, from what I understand of MacOS X and the physical layout of data on Mac hard drives, running defrag software can hurt. IIRC, people running Norton Speed Disk on MacOS X have reported problems. Let me put my $0.02 in about defragging. It is a Wintel solution to a Wintel problem. Being the worry-wort that I am, I periodically defragged my own Mac prior to MacOS X. I have never seen anything better than marginal improvement in the performance of my Macs. When I accepted my current position, I inherited a Mac-using secretary who never performed maintenance of any kind on her computer. I loaded Norton, ran through the utilities including Speed Disk. I saw no noticeable improvement. When I converted my Macs' hard disks from HFS to HFS+, the conversion left them in a most fragmented state. I ran Speed Disk--or was it TechTools Pro. At any rate, I saw no noticeable improvement after defragging. Even though I used it, I had become convinced that defragging was a waste of time. However, when I run Defrag on my Windows computer, the improvement in performance was dramatic. A computer whose performance had dropped to the point were it was barely useable was now performing as it should.

The takeaway message is simple: Defragging is an essential task to maintain the performance of [some] Windows computers. For Mac users, it is a waste of time or worse.

 

Nope. Some filesystems are intrinsically designed to basically never become significantly fragmented. Linux's ext3 is one such system, and hfs+ apparently uses a similar methodology (I don't know a lot about hfs+ internals; I'm relying on what I've read).

Of course, if this is really true about hfs+ I'm not sure why it would defragment smaller files on the fly...

Edit: Here's some interesting reading: http://docs.info.apple.com/article.html?artnum=25668