Do you need to defrag?
Well, it depends. Do you have an SSD? If so, no, you don’t. You’re not going to benefit from defragging. Do you have a regular spinning disk drive? Then yes, you’ll probably benefit from defragging. Contrary to what most Mac zealots will tell you, OS X doesn’t do all the defragging you need on the fly. If you write and delete lots of big files (videos?), you’re going to have a lot of fragmentation. I ran iDefrag and immediately found my 2009 MacBook Pro to have serious amounts of fragmentation. And it made sense, I download and delete large video files everyday. This creates huge holes in the table on the disk and thus it makes it harder for the OS to find the files I need even when doing simple tasks. I wouldn’t be surprised to find out that it contributes to the MacBook running hotter when playing HD video as well. Probably hurts gaming performance as well.
So you need to defrag…
So we’ve established you need to defrag. Is defragging going to help your two year old Mac that has put its HDD through the ringer with writing and deleting huge files? Well, it could…but you’d have to wait a very long time to defrag it. I ran iDefrag and let it run over night, and it only made its way through 3% of my drive. I don’t think it’s because iDefrag isn’t able to defrag quickly, but during the analysis iDefrag did on my drive it said my drive was over 90% fragmented. I eventually gave up on the idea of defragging the drive and came to the conclusion that backing up, formatting the drive and starting clean was my best option. At 90% fragmentation, it’s hopeless. Defragging would take days, it would be quite taxing on the drive, and after two years, I’d like to start fresh. My theory is, if you do periodical defrags on a freshly created OS X install, the defrags would go much faster and wouldn’t allow the drive to become as fragmented as mine did.
iDefrag has a few different modes of defragging. The more thorough the defrag process, the longer it takes. The biggest selling point that got me interested in iDefrag was its ability to defrag without a boot disk. Sadly, this isn’t currently possible under Lion. iDefrag works with Lion, but you’ll have to create a boot disk (which is easily created from within the app itself). Coriolis Systems, developer of iDefrag (as well as iPartition), have encountered a few problems due to Lion, and they said on their blog that they intend to issue fixes as soon as possible. These sorts of utilities are always going to have problems with major OS updates. Thankfully, you can still use iDefrag with Lion, you’ll just have to use a boot disk. You can download a demo here.