[X4U] Defragmentation, was Cause of kernel panics

[Jon Warms]

On Mar 15, 2005, Randy B.Singer <randy at macattorney.com> wrote:

> http://www.macattorney.com/ts.html
> Item #5 and Note #2
>
> I need to update Note #2 with some new defragmentation software for OS 
> X
> that has become available. The  most promising of these is:

I recommend a review of Apple's comments on Disk Optimization:

http://docs.info.apple.com/article.html?artnum=25668

which I read to say that defrag utilities are generally not needed 
because
Panther performs automatic defragmentation:

> 	▪ 	 Fragmentation was often caused by continually appending data to
> existing files, especially with resource forks. With faster hard 
> drives and better
> caching, as well as the new application packaging format, many 
> applications
> simply rewrite the entire file each time. Mac OS X 10.3 Panther can 
> also
> automatically defragment such slow-growing files. This process is 
> sometimes
> known as "Hot-File-Adaptive-Clustering."

If you create or edit very large files and your drives are almost full, 
the article
notes that your drives may be fragmented, and that a third party 
utility may
be helpful, and provides a link to a list of tools.

But in the general case, fragmentation may not be a problem, and
defragmenting some files may decrease performance:

> Mac OS X systems use hundreds of thousands of small files, many of 
> which are
> rarely accessed. Optimizing them can be a major effort for very little 
> practical gain.
> There is also a chance that one of the files placed in the "hot band" 
> for rapid reads
> during system startup might be moved during defragmentation, which 
> would
> decrease performance.

I guess that most users think of defragmentation for performance issues 
which I
think article 25668 addresses, or because they perceive hard drive 
problems.
If you have a file system or drive problem (that can't be fixed by a 
bigger drive or
adding a drive), first consider the condition of the drive. Hard drives 
included in
recent Macs are compatible with the S.M.A.R.T. index number, which is 
displayed
by running Disk Utility. The S.M.A.R.T. index number summarizes
the condition of the hard drive.

 From http://docs.info.apple.com/article.html?artnum=152059:

> If you see "About to Fail" in red letters, back up your disk 
> immediately and have the
> disk replaced. It will fail.

(Nothing ambiguous about "It will fail.")

If you choose to defragment, consider Apple's advice (from article 
25668):

> If you think you might need to defragment
>
> Try restarting first. It might help, and it's easy to do.
>
> 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.
>
> Another option is to back up your important files, erase the hard 
> disk, then reinstall
> Mac OS X and your backed up files.

Finally, a warning and a tip:

Before using any defragmentation program, verify the integrity of
the drive and back up any important files. The process involves copying 
and deleting
most of the files on the drive, so any problems can result in data 
loss. (From
http://www.macworld.com/2005/01/features/preventmacdisasters/index2.php)

 From article 25668:  If you use iMovie with Mac OS X 10.3 Panther, and 
FileVault is
enabled, performance issues can occur if your project is located in 
your encrypted
home folder (including the desktop). See iMovie: Using FileVault Can 
Affect
Performance.


Jon