So I'm confused and I need opinions on whether or not it's necessary to defrag mac hd's. I have a PB that I use a lot for moving large files (1-2 gig) and then delete them. I'm a recent switcher and previously with windows I would defrag my drive frequently (along with chdsk and scandsk). Is "repairing and verifying permissions" good enough for this (I don't even know what it means!). I would rather not get something like diskwarrior ($100) unless I was sure that it was worth it, and from searching the forums I get a mixed response. So in short, what do you guys do to keep your hd's optimized?