Disk Defragmentation and Drive Optimization: What Do They Do?

Defragmenting your hard drive is a lot like changing the oil in your car, something everyone has to do regularly. However, it is unexciting, inconvenient and therefore, very easy to put off. At least with oil change, most people understand the purpose. On the other hand, Windows doesn’t really tell you much about what defragmentation actually is. All you get is some vague statement about how Disk Defragmentation & Drive Optimization makes your drives faster. So what exactly is it?


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What Causes Disk Fragmentation?

Disk fragmentation is a result of the way a mechanical hard drive stores data. Consider a hard drive to be a very long sheet of paper. When you first install your operating system and copy files on it, everything is stored in a straight line starting at the top and working its way down. But over time, of course, you’ll start changing or deleting files and adding new ones. So suppose one of the files you delete is located closer to the top of the sheet of paper. Now, you have some free space that is right in the middle of a bunch of other data. Instead of being at the very end, like it was when you first started using your hard drive.

A fragmented DIsk

What happens to this free space? Well, suppose you put another relatively large file on your hard drive, your computer will place part of that large file in that free space until it’s filled up and then place the rest of the file elsewhere on your hard drive. This is called “File fragmentation” and it can seriously slow down performance in a mechanical drive because the platters have to physically spin to allow the drive’s head to access the files. And if a file is broken up into several parts, scattered all over your disk, it’s naturally going to take longer to bring up whatever it is you’re looking for.


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How Defragmentation Works

Defragmentation reverses the effects of fragmentation by doing two things;

1. Defragmentation reassembles any files that have been broken into little pieces and places them in just one physical location on your disc, resulting in faster access times.

2. Defragmentation rearranges most of the free space on your drive into one large continuous chunk. That way your PC will not fragment new files.

Disk Defragmentation and Drive Optimization
Fragmented vs Defragmented Disk

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SSD Optimization

You might be asking yourself; What if I have a Solid State Drive (SSD)? Defragmentation doesn’t result in the same performance benefits for SSDs it does for mechanical hard drives. Because SSDs do not have any moving parts, the PC can access all the data at roughly the same speed, regardless of which chip of the SSD is holding a particular chunk of a file. In fact, trying to defragment an SSD can do more harm than good. The cells that are contained in an SSD can only be written to so many times until they wear out and become completely useless. Defragmentation uses up a lot of those write cycles.

If you’re running Windows 7 or newer, Windows won’t let you defragment any connected SSDs. Instead, it will give you an option to optimize the SSD. This sends something called a “Trim command”. Unlike mechanical hard drives on which the data can simply be overwritten, the cells on SSDs have to be erased before new data can be written to them. Otherwise, you will seriously lose performance over time. Trim erases cells with old data that hasn’t been physically removed from the drive.

Disk Defragmentation and Drive Optimization
SSD Optimization

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This enables the SSD to write new information to those cells much more quickly in the future. Trim is usually handled automatically by Windows, so you don’t need to do much to keep it running. But if you have a mechanical hard drive make sure disk defragmentation is running periodically.

Now that you know what Disk Defragmentation & Drive Optimization are, go ahead and do it on that sluggish home computer your mother is always complaining about.