Can Apple Disk Utility defrag the hard drive?

Disk Utility doesn't defragment. We don't defragment drives anymore with OS X. Why do you think you need to?

Added this link on the subject


9. Defragmentation. Mac OS X does its own defragmentation as is noted by this article:

http://www.info.apple.com/kbnum/n25668

Message was edited by: Peter Bannon

If you run Disk Warrior and build a map it might show a 6% fragmentation say. Don't you get a performance boost if the fragmentation is zero? I also heard that if you have lots of large files on your system optimizing (defragging) is good. I don't optimize my system often but do it every now and then.

Apple KBase article [About disk optimization with Mac OS X|http://docs.info.apple.com/article.html?artnum=25668]

Two different views about defragmentation:

[Optimizing Disks Is a Waste of Time|http://db.tidbits.com/article/7254]

[Macintosh OS X Routine Maintenance|http://www.macattorney.com/ts.html#Anchor-31774]

The links above also have links to specific tools you can use.

There is a difference between defragmentation and optimizing. Defrag. makes files occupy contiguous space, optimizing puts things in a specific order and order that supposedly makes them easier to which to get access. Techtool has a defragmentation feature. idefrag mentioned by another poster also does optimizing.

Tiger automatically defragments files smaller than 20MB. I get the impression that the borderline between defragmenting actually helping depends upon how full your drive is and how many truly large files you keep on it. If you have maybe only 15GB or so free on your drive and you have a lot of 1GB video files then those are probably greatly fragmented. The degree to which that actually matters I don't know.

I quote this from another post:
BDaqua:
"iDefrag, SpeedToolsX, Drive Genius, and of course DiskWarrior that will defrag the Directory.

I use DW first, then SppedTool's Disk Defrag in that order."

"...If you run Disk Warrior and build a map it might show a 6% fragmentation say."

I don't believe DW is showing fragmentation of your hard drive. It graphs your directory.

I'd say if the bulk of your files are 8-30MB then they are probably already defragmented just by virtue of being near or under the 20MB limit. Even a 30MB file will probably only be in two or three chunks. It's when your 1000MB video file is in 1000 different pieces that you might consider defragmenting. However, if that is happening you are probably also creating that by not having enough empty space on your drive period and might need to consider getting a bigger drive.

There's an application called [Show Volume Fragmentation|http://www.macupdate.com/info.php/id/18451/showvolumefragmentatio n] that just reports fragmentation. Read the reviews. The other thing is that pretty much any drive will show some fragmentation, even one just defragmented. You also need to know how to read a utility like this and don't let it scare you into thinking you absolutely have to defragment.

The easiest and cheapest way to defragment is to clone (Carbon Copy Cloner, SuperDuper!, others) your drive to another drive, wipe the original drive, then clone back. Files are automatically defragmented when copying provided the target drive has sufficient free contiguous space.

Whenever the subject of disk de-fragmentation comes up, someone mentions DiskWarrior. DiskWarrior rebuilds directories. It does not touch the files. Although the terminology is similar, what DiskWarrior does is totally unrelated to disk de-fragmentation.

Also, referring to disk (not directory) fragmentation, it is not true that zero fragmentation is ideal. In that state, the files are all jammed up against one another, and have no room to expand. Any file that gets modified ends up with worse fragmentation than if the system was allowed to apply its own de-fragmentation strategy.

Plenty of good info so far, but would like to add, even if you do defrag your HDD, OSX will quickly fragment it again, the only real help in that area is giant HDDs where you have say 50% Free Space so OSX is more likely to instantly find contiguous space to write to.

I've defragged every which way there is, and it only lasts about a week, except DW defragging the Directory lasts longer.

I should not have been so quick to say we no longer defragment hard drives. Obviously some people do. I haven't since jumping from OS 7 to OS X (unix).

Fragmented drives used to be a real problem ( back in the 20 MB HD days)

OS X seems to take care of the problem. However I do clone and then erase my drive maybe every year, which takes care of that problem.

What is a real performance issue is contiguous free space. The OS uses free disk space temporarily as virtual memory. Just booting up in OS X 10.4.11 uses 10GB of virtual memory. And I have 5GB of RAM. Less RAM more VM