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What the Heck IS Defragmenting, Anyway? - And Why Do I Need To Do It?
~~ by Linda Johnson, Linda's Computer Stop

Originally published in TechTrax.  Reprinted here for those that missed it.

Note: This article is for new or inexperienced computer users and I’m going to explain this in the simplest of terms. However, more experienced computer people or tech people may want to share it with computer novices, in an effort to help them increase their computer’s performance.

Defragmenting is what you need to do when your files on your computer are “fragmented”. Fragmented simply means the files are broken up into pieces (or fragments). How does this happen? Let me explain.

Think of your computer’s hard drive as a dinner platter where all the files are sitting, waiting to be used. In this analogy, I’ll show you the dinner platter with peas (representing file clusters) on it.

When you first get a new computer and start to install programs or create files, they are added to the disk (platter) in contiguous (side by side, touching each other) clusters (peas), starting at the outside edge of the platter and continuing inward in a circular motion. So, the peas on your platter will look something like this:

Actually, there will be more peas than this and some of the peas will be in other locations on the platter (certain system files need to be located on specific parts of the drive). But, to keep this simple, let’s just concern ourselves with the files we create or install ourselves, and not those files created by Windows.

After a while, when you’ve been installing or creating lots of files, your platter starts to fill up with peas, and they are added, in a sequential order, around the platter, until it looks more like this:

When you want to use a file, your read/write heads in your computer look for that file by starting at the beginning of the drive and moving in a circular motion, inward, in the same order that the files were added. In this picture, the “fork” represents the read/write heads as it searches for the next “pea” you want to “eat”:

When all the files are in an orderly contiguous fashion and all the peas are complete, this goes relatively quickly. But, this doesn’t last long.

Eventually, you start deleting files and moving files. So, there are spaces between your peas and your platter looks more like this:

Well, there are gaps there, but the remaining files are still intact. However, the “fragmentation” occurs when you add NEW files. To understand this, I first need to explain cluster size and how it works.

Clusters determine the amount of space a file takes up on a disk. In newer computers using FAT32 or NTFS, a cluster size is 4KB. Only one file can be located in any one cluster. Therefore, if a file is only 1KB in size, it will still use 4KB of your disk space because it will take over that one cluster and the remaining 3KB will not be used by any other file. Similarly, a file that is 13KB will actually use 16KB of your hard drive space because it will take over 4 clusters. 4KB (uses one cluster of 4KB) +4KB (uses a second cluster of 4KB) +4KB (uses a third cluster of 4KB) + 1KB (which uses a fourth cluster of 4KB).

So, if we delete a file that is 45KB, we now have a gap between our peas which is 48KB in size because that file was taking over 12 clusters of 4KB each.

Now, let’s say we create a new file which is 90KB. This file will require 23 clusters which equals 92KB (23x4). So, our “fork” (read/write head) does its normal sequential, contiguous thing and starts at the first gap it sees between the peas. However, this gap is only 48KB, so it drops 48KB of the file there, then moves to the next gap. This gap is only 24KB so it drops a second piece of the file there. Then it moves to the next gap and drops the remainder of the file there. See the picture below. Each green pea is a 4KB cluster. Filling the gaps that you saw in the previous picture with red peas, you can see that a 90KB file will be broken into many pieces when it is added.

And, THIS is file fragmentation. A file that is split up into multiple parts is a fragmented file.

What does this mean to us in terms of our computer’s performance? Well, the read/write heads (fork) have to touch down many times when you want to access this file, instead of just once if the file was all in one place. When you tell your computer to open this file, the fork touches down to grab the first pea or peas, then lifts, then touches down again to grab the next peas, then lifts, then touches down again, and so on and so on, until it has all the peas that make up this file. Then, and only then, will the file open. This is more work for your hard drive, so it puts more stress on the drive AND everything starts to slow down.

So, when you run Windows Defragmenter, it finds all the files that are split up into pieces and moves all the parts to a location where they can all be together again, in one contiguous string. It’s much easier and faster for the fork to touch down one time and pick up all the peas at once!

If you want to know how to run Windows Defragmenter, just use your Windows Help Files. It’s all explained in there. Also, if you have something like Norton Utilities on your computer, you can use an alternate program. I like Norton’s Speed Disk program because it not only defragments, but it lets me choose my more important files and place them near the beginning of the drive. Since the fork starts at the beginning of the platter and works its way in, files that I use a lot load much faster if they are on the outside edge of the platter. However, beginners are probably better off just sticking with Windows Defragmenter until they know more about file allocation.

I hope this explains fragmentation for you and I truly hope, after reading this article, you will go to your Start button> Programs> Accessories> System Tools> Disk Defragmenter and see how fragmented your drive currently is and make defragmenting a part of your normal routine.

Linda Johnson is a college instructor of all of the Microsoft Office Programs, as well as Adobe PhotoShop and Windows. She also teaches online distance learning classes in Excel, Outlook, PowerPoint, Publisher, and Word at Eclectic Academy. She has worked helpdesk and teaches and lectures at many local businesses and tech schools in her area. Support this newsletter by checking out Linda's eBooks, MS Word MAGIC!, Book I: Fonts, Fun & Formats and Book II: Table Wizardry, How To Get Started As a Software Trainer, and her newest series of MSOffice eBook Tutorials and CD