I received an email from a client this morning with
that question. It’s good one for writing this
blog entry. First, here is a little background. James
purchased his first Macintosh a couple of years ago.
He is a long-time and very experienced Windows user.
The question of defragmenting hard drives also comes
from long-time Mac users who recently made the switch
to Mac OS X.
In the case of Windows computers and Macintoshes
running Mac OS 9 and earlier, over time, hard drives
slow down when the user tries to open, save or copy
large files. On those computers, files are stored
around the hub of the drive in the order in which
they were saved.
The directory file on the hard drive keeps track of
where files are stored and it keeps track of free
space.
When a file is edited, the new version is saved to a
different area of the hard drive. The directory is
updated, and the space where the old file was stored
is marked as free space.
When the user saves a file to the hard drive, the
directory looks for the first space large enough to
fit the new file and uses that space. If there is
extra space from the old file, that area is left
empty.
Over time, as files are written and rewritten and as
files are deleted, there are more and more little
chunks that are too small for new files to be written
into. Then the OS for the computer begins dividing
large files into smaller chunks or fragments to be
able to store them. The directory then has to
remember where the fragments are stored and it has to
pull them together when the file is opened or copied.
There are utility programs that can be used to clean
up this file mess. They are called disk optimizers or
disk defragmenters. They re-write the files stored on
the hard drive to put files of the same type
together. In the process they eliminate the free
space so that there is room for new large files. They
also put files that are stored in fragments back
together.
In Mac OS X, files are arranged in bands around the
drive, depending on their function. In between the
bands, there is free space for future files of the
same type. Defragmenting utilities tend to pack all
the files, regardless of their type, tightly around
the hub.
Mac OS X is written so that it uses some of its free
time to keep your hard drive organized. When your
computer is on but asleep, Mac OS X is working in the
background to defragment and rearrange the files to
keep your hard drive running at its best.
An optimizing or defragmenting program will rearrange
the files according to what its programmer thinks is
“right.” When you quit the program, Mac
OS X will take over again and rearrange the files the
way the engineers at Apple determined was
“right.” This is not good!
There are some drives situations in which it is you
want to use a defragmented drive. If you are trying
to capture audio and video files for serious editing
in programs like FinalCut or Logic, it is best to use
an empty drive as a working drive for capture and
editing. Because there are no other files, these
large files will not be fragmented as they are
written.
After you are finished editing the file, you move it
to a regular hard drive for storage and the working
drive is erased the drive with Apple's Disk Utility
before new files are added and processed.
It is also helpful to have an empty drive for
Photoshop to use for the temporary files it produces
as you edit images. If Photoshop is working
correctly, the temporary files are deleted when you
quit. If the temporary files are not discarded
properly, erasing the hard drive where the temporary
files are store can speed up Photoshop.
Apple has an area on its web site called Support. It
stores articles about questions like this one. This
article is a little old--but things have not changed.
If you would like further information, read:
http://support.apple.com/kb/HT1375
There are lots to things to know about Mac OS X.
While there are lots of articles and resources
available, some of us do better with hands-on
learning. If you would like a bit more help, consider
booking a tutorial session with me at
Dr. Mac Consulting. The cost is
$60 per hour and we will cover just what you
want to learn. Give us a call at 408 627-7577 or
send us a message at
urgentrequest@boblevitus.com.
--Pat
Tags: Troubleshooting