Defrag

Rhisiart

Rhisiart

Registered
HFS hard drives shouldn't need defragmenting. Occasionally if I want to boost the performance of my G4 I reformat the hard drive and reinstall everything.

However, I have just tried iDefrag. It claims it can justify defragmenting HFS hard drives, as long as it not done too often.

I have just tried it and the difference in performance is quite noticeable (as good as the alternative described above).

However, I wonder whether defraging a HFS drive is wise? Are there any potential pitfalls?
 
rhisiart said:
...

I have just tried it and the difference in performance is quite noticeable (as good as the alternative described above).

However, I wonder whether defraging a HFS drive is wise? Are there any potential pitfalls?
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I am struck by the fact that you post no benchmark figures for either before or after running iDefrag. "Noticeable" is not a quantitative measure of anything. As a Mac user since 1989 and having run optimization utilities up until I adopted MacOS X, I have never seen a performance benefit to defragging beyond few percent (3-5%).

The phrase that may apply in your case is Post hoc, ergo propter hoc.

After accepting my last job, I defragged my new secretary's Mac on which she had never performed any maintenance at all. There was no noticeable (that word again) improvement in performance. I had begun to believe that defragging was an urban legend until I defragged her Windows machine. The improvement was not noticeable, it was dramatic. It was as though I had bought her a new computer.

What harm can it do? Physical damage, probably none if your computer's hard drive is otherwise OK. However, Apple warns you that you defrag utility may change Apple's organization of the drive. This can be expected to reduce performance.
 
MisterMe said:
Post hoc, ergo propter hoc
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No I didn't data-benchmark my 'pre' and 'post' machine performance using iDefrag, just as I presume that you didn't benchmark your friend's PC before and after you defragged it.

Absit iniuria verbis
 
Apple made those warnings years ago, back when none of the available defragmenters were properly updated for OS X. iDefrag (and I think VolumeWorks and TechTool, too) respect the "hot band", where OS X groups certain files to improve startup time.

Certainly, there is a risk when using defragmenting programs. I've always advocated the old reinitialize/restore option, just because it's safer. Either way, make complete backups first. If something goes wrong with a defragmenting program, it's quite likely you'll wind up with an unusable volume. That actually happened to me the first (and only!) time I used iDefrag, several years ago. It essentially froze up, and after the better part of a day with no progress, I finally force-quit it. In the end I had to reinitialize and restore everything from my backups anyway.

I've argued the merits (and in some cases, lack thereof) of defragmenting several times on these forums. While I cannot recommend it generally, there's no question that sometimes the effects are huge. That said, I went almost two years without doing any defragmenting at all. It wasn't a problem for me, because after I had serious problems with fragmentation before that, I changed my habits so as to minimize the problem. That includes keeping a good amount of disk space free, and using multiple partitions to keep large, frequently-changing files from messing with my startup volume. I try to keep my startup volume as static as (reasonably) possible. Fragmentation is something I just don't think about anymore.

Recently I reinitialized and restored my drive (for other reasons) and there was no noticeable improvement.

A good rule of thumb when tracking down performance problems is: unless you have very good reason to believe it's fragmentation, it probably isn't.
 
Can't say I'd recommend defrag programs for OS X. I've never done it, nor have I seen any speed increase the few times I've clean installed when upgrading the system. Just doesn't seem to be an issue on OS X, even when dealing with large files daily over extended periods of time.
 
Apple:
If your disks are almost full, and you often modify or create large files (such as editing video, but see the Tip below if you use iMovie and Mac OS X 10.3), there's a chance the disks could be fragmented. In this case, you might benefit from defragmentation, which can be performed with some third-party disk utilities.
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http://docs.info.apple.com/article.html?artnum=25668
(If you do lots of video work, you should have an external drive to put your files on anyways)

Apparently, OS X will defragment some file automatically as well.
 
If a harddisk is full, defragging becomes a looooooooooong and tedious task. Try moving a 4 GB file around if you have 2 GB of free space, for example. ;)

1.) Repair permissions from time to time.
2.) Keep 10% or more space free on the system volume.
3.) From time to time, clone the drive to an external drive and then clone it back onto the reformatted main drive, but I don't really think it's necessary.
 
fryke said:
......from time to time, clone the drive to an external drive and then clone it back onto the reformatted main drive, but I don't really think it's necessary.
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SuperDuper! seems to do this reasonably reliably as I am sure other third party programmes. Does Migration Assistant do this well too?
 
rhisiart said:
No I didn't data-benchmark my 'pre' and 'post' machine performance using iDefrag, just as I presume that you didn't benchmark your friend's PC before and after you defragged it.

Absit iniuria verbis
Click to expand...

It would appear that MisterMe could use a good "defragging"


:D
 
MisterMe said:
That sir, was uncalled for.
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No, it wasn't - you have the tendency to be quite a pompous jerk
and i feel obligated to call you out for it........why, you may ask?

I recognize the behavior because i used to have the same problem,
and the reactions i got as a result helped me realize it. :)


*and don't call me sir - i work for a living!!!! :D
 
Now, now, boys... We don't call for defragging, we don't defrag and we try not to get too pompous over someone not delivering benchmarks. (Besides: When did we _ever_ write down benchmarks here on macosx.com when testing something. We've _always_ said things like "noticeable" or "better" or "slow as molasses" and were okay with it.) :p
 
MisterMe said:
That sir, was uncalled for.
Click to expand...


g/re/p said:
No, it wasn't - you have the tendency to be quite a pompous jerk
and i feel obligated to call you out for it........why, you may ask?

I recognize the behavior because i used to have the same problem,
and the reactions i got as a result helped me realize it. :)


*and don't call me sir - i work for a living!!!! :D
Click to expand...

You DO make a valid point - i was being a smartass - i could have worded my post differently.

Please accept my sincere apology! :)
 
I was surprised when Windows NT and NTFS arrived and they still needed defragmentation. Mainstream timeshared/server operating systems had pretty much eliminated fragmentation as a problem back in the '80s. Defragmentation seems like something from the bad old mainframe days, like manual cluster/cylinder management or preallocating maximum file sizes.

HFS+ isn't perfect by any means*, but I would be astounded if fragmentation is a real issue.

* I really wish Apple had followed through on their UFS update in Panther and switched from HFS+ to UFS as the default file system. Yes, they could have done that without losing functionality, by implementing case insensitivity and hooks for things like Spotlight in the vnode layer above the file system, like they do for network shares.
 
There has been a ton of misinformation about this topic on the Internet. So I researched it very carefully. You may want to have a look at:

Macintosh OS X Routine Maintenance
http://www.macattorney.com/ts.html
Item #6 and Note #1

There are a number of citations and some long-winded explanations there.
 
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