It may or may not effect non-Intel machines running Leopard as well. Definitely worth a look if you're interested in tweaking.Quick Warning: iDefrag doesn't currently work in Leopard due to a bug in Apple's AHCI driver on Intel machines. There's a section in the help guide that talks about the syntax in depth and it's pretty powerful. For instance, say you wanted to group all files whose name contains in “Barn” and that are between 10KB and 10MB in size into a single place or perhaps you want to place everything from the “/sw” directory in the same part of the disk. it uses the same classification engine used to color the blocks on the display, and can be configured using arbitrary expressions in a simple text file. The example they give:quote:As for the programmable optimization algorithm. One feature in particular that looks absolutely awesome is that the optimization algorithm is programmable. Performance since has been consistently improved for the past week and I can confidently say it was not a placebo or a quick, transient fix.More about iDefrag here. I immediately noticed a much faster boot time, much, much, MUCH faster application launch time, faster Spotlight lookup, reduced sluggishness switching between loaded applications.Keep in mind, I have 2GB of RAM installed and this is on a fresh boot. It's also the only defragmentation utility that I could find that supports the 'hot band' and will actually optimize it, as well.So I bought and installed iDefrag, ran Onyx again, rebooted, cloned my boot volume to the external drive, rebooted off the external drive, ran 'Full Defrag' in iDefrag on the main drive and then rebooted off of that.Free space fragmentation went down to 1.3% and probably would have gone lower if I reran Full Defrag for another pass.Results: Wow. And it's not just a defragmentation utility, it also does optimization as well. It's very configurable and much more power-user oriented than something like TechTool Pro. For its feature list, the price didn't seem bad. I decided to download iDefrag and take a look to see what my fragmentation situation looked like.In short: yikes.3.12% file fragmentation98.3% free space fragmentationFile fragmentation wasn't too bad, as expected, but 98.3% free space fragmentation is absolutely horrible and would have a definite, measurable impact on performance, particularly when it comes to swap usage.So yea, I figured I'd bite the bullet and see what iDefrag could do. Rebooted a couple times and there was a marginal speed gain, but nothing impressive. I haven't gotten around to installing Leopard on the test partition yet, but I was curious to see if there was an actual performance loss on this system or if I was just imagining one.So I went ahead and ran Onyx, let it clean caches, run maintenance scripts and rebuild my Spotlight index. So in the meantime, I got an extra HD that I'm using with SuperDuper! for backing up my main Tiger installation and for testing Leopard before I migrate my main system over. I've read a lot of reviews of Leopard saying how much 'Snappier' it was than Tiger, which got me thinking again about the performance of my own system.I've been eager to migrate to Leopard, but a couple key applications and workflow utilities I need still haven't been ported. For a while I have been thinking that it felt slower than when I first bought it, but I chalked that up to getting past the honeymoon phase of having a new machine.

I've never reinstalled OS X on this system. It was one of the first ones to ship when the Intel Macs first debuted. bakshi mentioned disk fragmentation as one possible culprit and ManxStef suggested iDefrag as a possible solution.I've had my MBP for almost 2 years now. A few suggestions were rebuilding the Spotlight index, running Onyx to clean caches and run maintenance scripts, uninstalling 3rd party add-ons, etc. A few weeks ago, hux posted this thread asking for possible explanations for and solutions to an OS X install slowing down over time.

Idefrag boot disk