Why Should I Defragment my Hard Drive?

Defragmenting (or ‘defragging’) is a way of literally tidying up your computer to make it run smoothly. It works by physically moving the files on your hard drive so that your computer can quickly access them.

Think of your computer like a bedroom floor. If you let things get too messy, it slows you down. You don’t have enough floor space in anyone place to get anything done. It takes longer to find things. And things that should be together – like a pair of shoes – wind up in completely different places.

A computer can easily end up in a similar situation. Each time you create a new file, your computer usually tries to physically store it as near to the start of the disk as possible so it’s easier to reach. However, if you delete the file, it will leave a gap. And if you alter the file (for example, editing a document), it may no longer fit in the original space, so it will be moved elsewhere, again leaving a gap. This gap will usually be filled with the next new file that fits into it.

As the files get scattered about, the disk drive will take longer to find and read them. It only adds on a few thousandths of a second each time, but because computers process so many files, this soon adds up and your computer will become noticeably more sluggish.

Windows has a built-in defragmentation utility. You’ll find it by opening your Start menu, going to Programs, selecting Accessories and then choosing from the System Tools. (The defragmentation utility is also an option if you run the disk clean-up service by right-clicking on your drive in Windows Explorer and selecting Properties.)

When the utility runs, you can choose either Analyze (which will check whether your drive needs defragmenting) or simply start the defragmentation right away.

While your computer is defragmenting, you’ll see a map of your disk drive showing how it’s rearranging the files. The main things it does are moving all the file indexes and directory details to the middle of the disk (meaning the disk drive can access them more quickly), moving little used files further away, and putting related files next to one another.

Defragmenting is a lot more effective and runs quicker when you have more free disk space. (Imagine how difficult it is to tidy a messy floor when you haven’t even got enough room to move anything.) So you should delete any unnecessary files and empty your Recycle Bin before you start.

You’ll also find that defragmentation takes considerably longer when you have programmes running. That’s because your computer is doing the technical equivalent of cleaning up a room while children are still playing in it! So it’s best to close down all your programs first – use the Task Manager’s Applications list to check there aren’t any running that you can’t see.

Even with no other programs running, drefragmentation can take several hours, so it’s usually easiest to do it overnight. If you do this, you may need to temporarily disable any programs (such as anti-virus software) which are scheduled to run a scan of your computer during the night so that it doesn’t wind up getting in the way.

As Ashwin Satyanarayana says in his excellent article on Defragmentation Myths, though defragmentation can feel like a hassle the first time you do it, it’s worth doing it fairly regularly. After all, just like tidying a room, the longer you leave it, the longer it takes when you finally get round to it!

Other related content:

How To: Defragmenting Your Hard Drive in Windows