Is defragging on OS X necessary?

I've been looking into getting idefrag for a while now. But a lot of other places I've read says OS X itself tends to fragment files a lot less then one would expect. Also I've never fragmented my imac in 4+ years of owning ti and have had no real noticable slowdowns cause fo the issue.

1. Is defragging necessary on OS X (10.6)?
2. Is there a potential to kill my hard drive by defragging? (Just asking so I can have the Time Machine backup ready just in case)
3. If I do defrag would the HD improvements be worth it? Or would it be so small it's not worth the effort?

No defragging is not necessary on the HFS filesystem used by Mac..unlike FAT filesystems used on Windows, the information is stored in a manner where the data isn't fragmented..

You wouldn't necessarily hurt it by defragging it, but it's unlikely that you'll see any improvement or difference either..

So just run Disk Utility to fix any issues you might have, but beyond that..let it be..

If it ain't broke, don't fix it..

Regards

You can download iDefrag. The download version will give you a report of the fragmentation of your drive. I have yet to see above 0.5% the few times I've checked.

OS X keeps your files in good shape. What it doesn't do is maintain contiguous free space like you would be use to seeing with the better windows defraggers. For those with close to a full drive and do a lot of storing then deleting of very large files (GB or larger), then a defrag might come in handy.

The downside to iDefrag, is that to defrag the drive, you have to do it from a separate startup disc and leave it to run all night - it takes hours. To me, if you are in the small percentage that a defrag would pay off, think I'd just use SD! or CCC and reclone back to your internal drive which would basically do it for you in a fraction of the time.

The vast majority of users, especially those like myself that maintain that 25-30% free space minimum should never need to do it.

I took your advice bobtomay and downloaded the idefrag demo just to see how defragged my hard drive is. And I've had my new imac hard drive for about 2 months now and my frag rate is about 0.1%. So I get your point.

But the CCC/SD thing is a good idea.

I have bought iDefrag and found it did help my Alum iMac that is always about 65% full. I played over Christmas with TM, iDefrag and restoring after doing end of month maintenance and backups to DVD archiving. I loaded Snow Leopard and then returned to Leopard as some of the required program upgrades were not ready for day to day production IMO.

I read somewhere that very large files are not dealt with when the OS does it's business. I am a Graphic Designer with lots of Photoshop and large movies so it did help the machine's performance IMO. What I did see is that when performing a full backup from Time Machine, TM records sector by sector and returns the drive image the same way. I used IDefrag prior to TM and the returned files when needed were in pristine shape.

I feel that iDefrag is a worthwhile tool in maintaining your iMac for the price it is.

The downside to iDefrag, is that to defrag the drive, you have to do it from a separate startup disc and leave it to run all night - it takes hours. To me, if you are in the small percentage that a defrag would pay off, think I'd just use SD! or CCC and reclone back to your internal drive which would basically do it for you in a fraction of the time.

Click to expand...

The new iDefrag version 2 no longer needs a separate boot disk to work. When started, it reboots into a special mode and allows the defrag process to be run.

Regards.

About the only time I have needed to defrag the drive has been before creating my Boot Camp partition. The setup assistant refused to complete because it could not find sufficient contiguous free space. Unless you are working with large files you aren't likely to have a problem.

BTW If you choose to defrag your drive make sure things are backed up. As Bob points out this can take a great deal of time. If anything goes wrong (power failure etc) your data can be ruined.

chscag said:

The new iDefrag version 2 no longer needs a separate boot disk to work. When started, it reboots into a special mode and allows the defrag process to be run.

Regards.

Click to expand...

Thanks, had read that once before, but I have to be told 3 or 4 times nowadays for it to stick. ;D

About once a year, I do the following:

1. Make a bootable clone of my entire hard drive using Carbon Copy Cloner. (actually I do this regularly but nevermind)

2. Boot from the clone to make sure everything is working as expected.

3. While still booted from the clone, I *erase* the boot drive. In fact, I zero it out (under "security options" in Disk Utility). This takes an hour or so (320GB drive).

4. I think use CCC to clone BACK to the now-erased boot drive.

5. Finally, I boot from the "refreshed and defragmented" drive and, usually just for laughs, run OnyX on it.

The entire process takes about three to four hours depending on how much attention I'm paying to it. After a year's use, yes I do notice a "spring in its step" after doing this, but not a huge one.

If you really want to keep your Mac drive humming along beautifully for years on end, there are four "tips" in my experience:

1. Keep plenty of free space available. At *minimum* 12GB, more if you have excessive amounts of RAM (since the system will use drive space as virtual RAM when needed). OS X works best (including its own self-defragger) when it has lots of free space to work with for temp files etc.

2. Run something like OnyX periodically. I used to prefer AppleJack, but alas there is no SL version. By "periodically" I'm thinking once a month-ish.

3. Optionally, you can do the method I've described above to "refresh" your drive.

4. MAKE BACKUPS. With the price of hard drives being so cheap these days, there's no excuse anymore. I make two backups to two drives: one is a Time Machine backup, the other is a clone backup. TM takes care of itself, and the clone can be scheduled regularly as well (doesn't need to be done all that often, maybe weekly, if you're also using TM).

well explained chas_m

+1 for that chas_m. Pretty good advice there. I tend not to run Onyx much. Not that it's a bad program I just tend to reserve it for when I am experiencing a problem.

Oh that's what you shouldn't do with Onyx. It's more a prevention app then a cure app. As the above have all said use it from time to time and all should be good.