Defrag - iMac

Depending on what you do, it may not be necessary . . .

Drive Genius 2 and DiscWarrior are supposed to be good applications. But there is a down site. In order to defrag the internal disc you need to boot from a CD or DVD. And the current versions of these apps from what I was told from their tech support is that it won't work until Apple releases the Leopard DDK.

SRXguy wrote:
Which program would be recommended to defrag and optimize the hard drive of my Intel based iMac?

In general it's not necessary to defrag OS-X and in some cases can result in poorer performance.
I would also consider it mandatory to have a complete backup of OS-X before attempting to change the files structure with any 3rd party software.
I have been running OS-X since I got my first G5 and have never defragged any of my three boxes nor found it necessary to do so.

1. Disk Warrior is not for disk defragmentation. It repairs and optimizes the Directory only, a small partition dedicated to 'mapping' all the files on your hard drive. While it is an incredibly useful utility and solves most of the serious drive problems which might result in file loss on the Mac, it has nothing to do with disk optimization.

2. I've never heard the assertion that defragmenting might actually result in poorer performance. Hmmm...

3. Do a backup before defragment... absolutely!

4. Use iDefrag... http://www.coriolis-systems.com/iDefrag.php

5. It's true that the average user may never need to defrag their Mac but if you deal with large Photoshop files or edit video, for example and don't have a dedicated hard drive for scratch files, occasionally defragmenting the drive makes a big difference.

6. To read a cogent discourse on the issue read entry #6 on this page which relies on the knowledge of Micromat technicians (TechTool Pro etc.) as authoritative sources...

http://www.macattorney.com/ts.html#Anchor-31774

Welles Goodrich wrote:
1. Disk Warrior is not for disk defragmentation. It repairs and optimizes the Directory only, a small partition dedicated to 'mapping' all the files on your hard drive. While it is an incredibly useful utility and solves most of the serious drive problems which might result in file loss on the Mac, it has nothing to do with disk optimization.

2. I've never heard the assertion that defragmenting might actually result in poorer performance. Hmmm...

I thought I had read that in this forum. Maybe somewhere else. Something about moving some files that should not be moved. It may have been for an earlier defrag app.
Personally I would not want to disturb a working journaled file system. "If it ain't broke, don't fix it."

While cloning file-by-file and restoring will not defrag individual files, it will restore them to the HD without leaving "ends" floating around on the drive, which is one of the causes of BootCamp failing to partition the HD.
I have been using Unix systems for many years, from mainframes through Linux and BSD, and I have never defragged one of them.
For all the years *nix has been around, were it necessary for routine defrags, I am sure a program would have been included, since everything but the kitchen sink does seem to be under the hood 🙂

It's not correct to lump Unix systems together when discussing fragmentation, it all depends on the filesystem, and how the OS uses the filesystem. The OS X filesystem is completely different from the FS on any other Unix or Unix-like OS.

That said, I'm not convinced that fragmentation is an issue for many OS X users, despite the claims of the few companies trying to sell defrag software.

Hi Nerowolfe,

Where defragmenting a drive still is valuable for Macs is when the user deals regularly with large files which require contiguous space for writing/reading... particularly scratch or whatever they call their temp files. It keeps the drive from flailing about trying to place and then find parts of the files required for computations. Photoshop and other high end image editors, sound creation, 3D and video manipulation applications require large blocks of contiguous space for behind the scene computations, often from 6 to ten times the size of the actual saved file size.

I don't suggest 'regular' defragging as such as Windows benefits from, but occasionally that process will result in noticeable speed increases when one deals with large files (from 20mb into the multiple gb range) on a regular basis. For me, about twice a year when a new system upgrade is released, prior to installing, I'll clean out temp files, repair permissions (which also gets done weekly along with regular maintenance script activity), clone a bootable backup, install the new upgrade and then defrag my primary boot drive. For me it makes a significant difference.

Also, although the Mac OS is built on UNIX and even gained certification with Leopard, the file system is an oddball hybrid. You might enjoy the article I referenced at the end of my first post.

Cheers!
Welles

Interesting article. Thanks for the link.
I would point out that the idefrag program it links to only supports Tiger filesystems
http://www.coriolis-systems.com/iDefrag.php

I would get a new larger drive if I ever got close to 80% usage.
Many people avoid this problem by putting their large files on an external drive.
Another solution is to partition the internal HD and use the non-OS partition for the files, so as not to fragment the OS files.
With FW800 and Sata external drives today, many in the terabyte area, I would suggest using an external drive for video and other large files for several reasons: not just the fragmentation issue, but also to keep the wear and tear down on the internal drive, which is far more expensive to replace than an external one. At least for a notebook.
For a desktop, I would strongly recommend a second internal drive for these large files.

Message was edited by: nerowolfe

Good advice. Personally I have 4 internal drives and three external on my Mac Pro (one FireWire 800 for Time Machine and a couple of eSata run off a Newer eSata extension) but then I need to keep a number of Mac OS versions running because I do tech support for a number of families... one is still using Jaguar and they're happy with it for their basic computing needs.

I used to defrag my drives about once a month with OS 8 and 9. For those older OS's, it really did help. In OS X, I can't say I've seen any notable difference since OS X will automatically defrag files above or below a certain size (can't remember which way).

I bought Drive Genius a while back because it includes a defrag feature. It took a couple of times to notice that it actually damaged files on the drive it defragged. The computer would act strangely, get beachballs where I wasn't getting them before, programs suddenly crashing, etc. I'd restore the drive from backup and all would be fine again. Needless to say, I don't use it for defragmenting anymore.

I timed Drive Genius the second (or third) time. Then I erased the drive and restored it from backup. Then I did what would be defragging the old fashioned way. Cloned the main drive to an empty external partition, booted to that, erased the main drive and cloned it back. It actually took less time to do two clones than to run the defrag software. The end result is the same, files are written one at a time contiguously until done.

If you do use a large partition strictly as a scratch drive for Photoshop, Final Cut or the like and keep nothing else on it, you can "defrag" it simply by doing a quick erase with Disk Utility. With the file table wiped clean, the OS will write everything contiguously, regardless of where any files may have been before.