Hard DriveAs a consultant specializing in Mac OS X, clients sometimes ask me if they should “defrag” their hard drive. I always tell them the same thing: NO.

First, a little background. When a personal computer saves a document, it doesn’t always create a single entity on the hard drive. Instead, it divides the file into a collection of smaller chunks that are linked to one another. This gives the computer’s operating system flexibility in how it manages space on the drive. Consequently, you’ll be able to store files that are larger than the biggest single unused space.

Computer Files are like Waffles

Eggo big box

Think of your refrigerator’s freezer filled with frozen food. You look inside and find that you’re out of your favorite Eggo Frozen Waffles. So you head to the local big box store and buy the giant box that will feed you a month’s worth of breakfasts. But there’s one problem. It won’t fit in your nearly full freezer!

You have a couple of options.

  1. Throw out some of the old freezer-burned food that you don’t need or want.
  2. Rearrange what’s left.
  3. Open the 60-count box of Eggo Waffles and repackage them into smaller plastic bags for more efficient storage.

In the personal computer world, it kind of does the same thing — except it will start with option three first: dividing the file into pieces and then squeezing those pieces into the available spaces.

Hard disk defragging — a.k.a. disk optimization — is the process of rearranging all of a file’s fragmented pieces into a single contiguous location on the hard drive. Theoretically, this makes accessing the file faster since there’s less mechanical movement necessary to locate and read all the individual file parts.

So that’s seems like a good thing to do, right? Then why do I recommend against doing it for a Macintosh system? Let me count the ways:

  • Disk optimization involves an intensive movement of files. If you’re going to do it, I strongly recommend backing up your entire drive before beginning, since an error or power failure during the process could lead to disastrous results. Unfortunately, I think most people don’t bother to backup first. That’s a risk you don’t want to take!
  • Today’s hard drives are big and cheap. That means there’s less chance of a large file being divided up across a large area of your disk. Think of the frozen waffles. If you had a huge walk-in freezer, you wouldn’t worry too much about having to rearrange your frozen inventory to store the Eggo waffles — even the Sam’s Club giant size.
  • Mac OS X 10.2 and later has smart file allocation algorithms. It intelligently keeps larger files together.

The Bottom Line:

Defragging your Mac’s hard drive is not worth the time and risk involved.

And if your Mac OS X hard drive is almost full, getting a bigger drive will improve your performance much more that optimizing its cramped contents.