Years ago, I was a technician for an office that distributed important information via sneaker net. Meaning, of course, that this was before we linked everything with cables, and information was passed around via floppy disk (remember those!). Without fail, once a week or so, someone would bring in a floppy disk that they could not read, and into the old disk doctor we would go. We would defrag the disk, using a utility that looked just like iDefrag from Coriolis Systems… except, of course, that this was ten years ago. That was my first impression at launching iDefrag, a total throw back to the mid-90’s.

iDefrag does have a nice interface, with very simple to understand controls, and an interface full of pretty colors that are fun to watch. Each of the blocks in the interface is supposed to represent a block of data on the hard drive. I was at first alarmed at how badly my disk was fragmented, as indicated by the amount of red blocks that were viewable. But then, the next question that popped into my head was, “why?”

I’ve always heard that the lack of a file defragmenter on OS X was a good thing, due to the fact that the HFS+ file system handled fragmentation automatically. This idea was enforced after my research. Amit Singh, writing for writes this as the conclusion of a very detailed paper:

“Defragmentation on HFS+ volumes should not be necessary at all, or worthwhile, in most cases, because the system seems to do a very good job of avoiding/countering fragmentation.”

Apple themselves say that fragmentation is nothing to worry about on an hfs+ drive on this page where they say:

“You probably won’t need to optimize at all if you use Mac OS X.”

So why would I need iDefrag? For the most part, you probably don’t. However, if you work with a large amount of video files, and are willing to purchase the app and go through their… rigorous licensing scheme, then iDefrag just might be for you. HFS+ automatically defragments files that are under 20 MB, but it does not defragment anything over that amount. Coriolis Systems does a great job at explaining their side of the story, but I remain unconvinced.

The performance of the app is also worth noting quickly. iDefrag froze once during a defrag of an external USB drive, and refused to defragment an external firewire drive. The latter could have been caused by a lack of available space, but for the former I had no excuse. The app will not completely defragment your boot partition unless it is un-mounted first, requiring you to be running off a CD or using your Mac in target disk mode and running iDefrag from another computer. Which, after going through their licensing I was reluctant to do.

Bottom line is, if you feel that defragmenting your HFS+ formatted drive would improve performance, then iDefrag is for you. And, it does have a very nice interface, even if it does make me want to party like its 1995.


Eugene Kriegsmann

Back on to this thread, I am amazed at the reaction of Macheads to the idea that you might need to use a third party utility to resolve issues like fragmentation. I have had several discussions with otherwise rational people who simply cannot accept that Macs aren’t perfect. Hey, I love my Macs. I wouldn’t trade them for the world, but somethings need to be dealt with beyond what comes in the box. It doesn’t diminish the wonderfulness or make a Mac more like a Windows computer. It is just a real issue that needs to be dealt with in a rational manner, buy the software, install it, use it periodically. It isn’t sacrilege. You will not be struck with lightning or have Steve Jobs come by your house and slap your wrist. In short, get over it. It is a computer, not a religion.

Eugene Kriegsmann

I don’t want to hijack this thread with irrelevances, but just one comment. If my hard drive fails I am not going to pay Apple or anyone else $500 to replace it. I replace hard drives in PCs and laptops all of the time. It just isn’t rocket science Admittedly, the iMac is a bit more complex than a PC, but so is a laptop. If you don’t learn to repair your own equipment you are always going to be a victim, with PC or Mac.


Yeah micorsoft really sucks but i just bought a nice new quad core for $1300 and any mac around the power i got would at least be around $1800.  Its just that apple markets for cash money.  The i mac i was just on had a hard drive failure and it wasnt even 2 years old.  I looked into other sites and it seems that apple makes this happen to alot of people.  2 years and they charge almost $500 to replace a hard disk.  Ridiculous!  Im gonna do it for around $80.  OS X is a nice operating system I will admit but PC’s hold the market and their programs always have alot more too them. (Plus the fact i can finnaly play video games)   Windows is unstable shit but Vista is really nice.  But again i will admit if windows was in an os x enviroment the world would be a better place.  But Mac’s are really expensive and PC’s are not.  Its just sad to see how badly people get gouged buying a mac. Just compare a pc to a mac with the same parts (and dont forget the video card) and youll see.

Eugene Kriegsmann

I have found over the last year that my Intel iMac has gotten slower and slower. It is the old boil the frog routine. I ran the trial version of iDefrag yesterday and was appalled at what I found. I own a Windows XP computer as well, so I know what a fragmented hard drive looks like. There wasn’t major fragmentation, about 1% (160 GB drive about 80GB used). The biggest problem was that the OS and other files were spread all over the HDD. There were very few gaps of any size. I spent the $35 on the Coriolus site. I ran the program which took about 5 hours to defrag and another hour to compact the files. There was an immediate improvement in the performance. Just as an example, opening iTunes could take as much as 30 to 40 seconds prior to defrag. It opens now in under 10 seconds which includes opening contact with the Airport Express basestation. Other utilities and programs are comparably speeded up. I type a lot, so I notice when the machine lags. It has been lagging, but no more.
You make your own choices, but don’t belittle something without trying first. I have no problem with Apple not including a defragging utility in OSX. I don’t mind paying for one. What I object to is being told it isn’t necessary when it obviously is necessary. How many years did Microsoft ignore viruses and other problems with their OS and tell us that registry cleaners weren’t necessary? If there is a problem that can be solved by third party software share the wealth and be honest.


Well im a PC user trapped from being able to afford… Im on the Intel Based mac anyways… Aside from that why these issues of minor system performance dont seem like much to the average mac user. These utilities to fix the system should be free. and with windows when the defraggers going on a hd that actually gets serious traffic ran through it, the difference is highly noticeable. Comparing im trying to play videogames on my system and not your average 1997 run of the mill task. Well my point anyways since ive been rambling is that Mac’s are more unstable and the timing is very consisten to teh chrashing time in all the games i play. Constant writing and deletion of lage mac volumes with high “traffic” of files every day make it run very slow. let alone trying to run a video game. The mac disk defragmenting tool helped my OS X performance a lot. But the fact that I had to pay to defrag my drive… (IN WINDOWS ITS PART OF THE SYSTEM – YES THE DISK DEFRAGMENTER IS FREE AND MUCH MORE EFFICIENT THAN idefrag) and then learn i gotta use a stupid boot disk to do the full defrag made me wanna punch the mac. But I realize now that mac’s OS X is controlled by PC parts. And if you can seriously run a computer:
-boot up windows on your Intel Based Mac
-and if you know how to run windows
-Run WINDOWS on your Mac
your Mac being ran on windows will be much more stable. True Story… look it up. :From a stoner PC Facist… Sorry to anyone who got this far… and most likely I don’t make sense and please don’t get depressed cause I’m right. Well peace I’m running too much at once and my comps lagging….


(8/25/07) I just downloaded this to defrag as well as compact my files to the beginning of the hard drive. I need the room to run bootcamp and partition for XP Pro. I cannot get the boot disk to burn. I get an error stating “make sure you have enought space on the disk…….” Anyone else having the same problem?


Nice review. I like the fact that it pretty much says to not use iDefrag, and that you’re an idiot if you do.


I’ve used iDefrag for a while now.

First of all, the licensing isn’t any more rigorous than most.

Secondly, of course you have to unmount a volume to defrag it… you can’t be writing to the disk while you’re working on it.

I have noticed a significant difference in boot speed and application launch based on iDefrag’s hot-zoning. I was quite surprised. This is on a Pismo with a G4/550 card and a 7200rpm drive.

Josh Pigford

If you have opinions about something other than the article’s topic, email us or post in the forums. This isn’t the place for it. Future comments that aren’t on topic will be deleted. Thanks.


Mathue: I think I’m on board with Jeffrey here. Poor grammar and incorrect spelling do nothing for the legitimacy or trustworthiness of a source. If a source cannot even get spelling correct, what else is wrong with an article?


Editing isn’t something one finds on blogs typically. Ideally one should write their article up in a word processor but this is not the common way of blogging. The idea is that you get your text out there as fast as possible, thorns and all. Personally I can get the full gist of the article even though there are several errors.

As for performance..

In my experience with defragging OS X it seems to make little discernible difference in performance in relation to the time used to perform it.


err.. no offence but how about doing some tests if it really helps performance? or at least a subjective opinion i it did?
one can hardly call it a review if the main point of why anybody should use the app gets untested (well data freezes on any disk tool makes it a nono anyway, but still).

Shomei Ageradi

Good point chris.
This cannot be a review or it is a very bad one.
What’s the point of writing such a long article on a (mostly) untested software.

The title should not be “idefrag” but an indication that the article is more about misc. stuffs and a small talk on the need to defrag HFS+. There is strictly no information with idefrag that we couldn’t have obtained while using the demo version. (except for the hassle of registering which is quite repelling)

I think most people that comes here are looking to know if the software is worth buying.
So like chris, I ask “no offence but how about doing some tests to see if it really helps performance?”
You did buy the software after all. Why not use it ? (full defrag, booting on CDRom)
Everyone else would be grateful and they would stop complaining on the quality of the review.

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