From Apple:
Do I need to optimize?
You probably won't need to optimize at all if you use Mac OS X.
Here's why:
Hard disk capacity is generally much greater now than a few years
ago. With more free space available, the file system doesn't need to
fill up every "nook and cranny." Mac OS Extended formatting (HFS
Plus) avoids reusing space from deleted files as much as possible, to
avoid prematurely filling small areas of recently-freed space.
Mac OS X 10.2 and later includes delayed allocation for Mac OS X
Extended-formatted volumes. This allows a number of small allocations
to be combined into a single large allocation in one area of the disk.
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."
Aggressive read-ahead and write-behind caching means that minor
fragmentation has less effect on perceived system performance.
For these reasons, there is little benefit to defragmenting.
Note: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.
Disk Warrior will optimize your disk along with repairing the
directory structure. It was a valuable tool when I had system 9 or
before. I have not had a need in the several years I have used OS X.
Winsor
Long Beach, California, USA
On Mar 20, 2007, at 2:47 PM, Chuck Norcutt wrote:
> Whether journaling is enabled or not is not the issue. I was only
> trying to point out that Mac's are not immune from fragmentation
> issues
> and they are not. Most likely what saves everyone today (at least on
> the desktop) is humongous disks which rarely get near full.
>
> I don't mean to get into file system implementation here but I would
> hope that any defragger would also implement or work in concert with
> some form of journaling. I don't know why journaling would be
> considered incompatible with defragging.
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