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A Beginner’s Guide to Disk Defragmentation in 2020

By Emmanuel Dairo | July 17, 2020 |

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The main hardware components of your computer – the processor, memory, and internal storage – work in tandem to enable you to access files and load programs. While the RAM and processor do their work at lightning speed, the internal storage, especially if it is an HDD, sadly lags behind.

Due to its physical limitations, a typical hard disk drive is very slow and cannot keep up with the processor speed. Solid-state drives, while much faster than mechanical drives, still work at crawling speed in comparison with the latest chips. As a result, reading and writing data can be excruciatingly slow processes, especially when the process of natural file fragmentation steps in and worsens the situation.

This is why defragmenting your hard drive is necessary, even in 2020. It reverses file fragmentation and helps to improve computer performance. If you have previously come across the topic and found it couched in arcane language and opaque computer-speak, you will find this article both refreshing and illuminating.

The truth is that disk defragmentation is not so much a complex subject as a poorly explained one. To fully comprehend what defragmenting a hard disk entails, some concepts like fragmentation and the Windows file system need to be understood. Knowing how the traditional hard disk works and how SSDs are different will also help you to know why the former should be defragmented for optimum performance while the latter will do just fine without it.

First, let’s explain how the hard disk drive stores and reads data.

The Hard Disk

The hard disk drive has come a long way from IBM’s mechanical monstrosities of the 1960s to the compact storage devices with speeds of 7200 RPM we use in 2020. However, despite the constant improvements in both speed and size, one simple fact about the HDD remains in 2020: it is slow.

It is slow because it consists of moving parts like the spinning platters and the read-write head. These moving parts mean that there is a limit to how fast requests sent by the processor can retrieve the necessary data.

To further slow things down, not all the data that needs to be retrieved will be in the same location all the time. It may help to think of the spinning platter as a composite disk made up of several concentric disks. Let’s say four disks collectively make up the platter. Each disk is called a track, and each track is divided into portions of similar length called sectors. The number of tracks and sectors varies by model, but a single sector is usually 512 bytes in size.

So, why is this important? There are two main reasons. The first is that data stored on the outer tracks and sectors is accessed faster than data stored on the inner tracks and sectors. The second reason is that each unit of space on a hard drive is made up of a certain number of sectors. This unit is called a cluster. A cluster is the smallest unit of space on a hard drive that a file or part of a file can be stored in.

This brings us nicely to how Windows organizes and controls the data on hard drives — the NTFS file system.

The NTFS File System

To put it simply, a file system is the way an operating system arranges and manages the files on a disk. All the versions of Windows you are familiar with use the NTFS file system to organize the files on an HDD or SSD so that the system can access any requested data.

Drives that use the NTFS file system usually group the sectors into clusters consisting of 8 sectors each. This means that each cluster on an NTFS drive is usually 512 x 8 = 4096 bytes in size. If you save a 2MB file to an NTFS drive, it will be saved as chunks of 4096 bytes each on the drive. (If you care about the math, that means the 2Mb file will occupy approximately 488 clusters or chunks of space on the hard disk).

How Defragmentation Happens

Now that you know that each file you place in your computer storage is broken into chunks, it should be easier to visualize how fragmentation happens. Say, you save a 5MB file to a drive with lots of free space; the file will be broken into chunks as usual. The chunks will likely be placed next to one another, which will make them contiguous. This means that when the processor requests that file, the HDD will be able to retrieve it faster.

Now, think about saving the same file to a drive with not so much free space. Your system will save the file to the nearest available space. If that space is sufficient to contain all the file chunks, great. If not, the system will place some of the chunks somewhere else. The parts of the file are now separate from one another. Storing chunks that together make up a file in non-contiguous spaces on the hard drive is what is known as fragmentation.

Given that most of us regularly save files, some of which are quite large, to our hard disk drives, fragmentation is an inevitable and natural consequence.

Disk Defragmentation: Why Do You Need It?

The more files are saved on the hard disk and the bigger each file is, the more work the system has to do to read and write data. A disk drive full of large files means that there will be fewer and fewer contiguous locations to save each file until a point when there is simply none anymore. When this happens, the system simply saves different chunks of each file to whichever space it can find. The bigger the file is, the more chunks of it there are and the more scattered they are. Thus, when the file is requested, the read-write head has to jump around the various locations to assemble the disparate and scattered chunks. This process involves a lot of work and consequently takes longer, resulting in lower performance.

Apart from this, because the files are scattered all over the place, available space on the drive is also scattered. This in turn causes large incoming files to be immediately fragmented since no contiguous chunk of free space is available for them to be saved to.

Although the read-write speeds of modern HDDs have improved tremendously compared to earlier in the decade, disk fragmentation means the speed will decrease with time, also slowly leading to hard disk degradation.

This is why you need to defragment a disk drive regularly.

Luckily for most of us, modern operating systems like Windows 10 have a defragment schedule that runs regularly and takes care of your hard drive. However, this system can stop working or break down, so you need to know when your system needs immediate defragging.

There are some tell-tale signs and symptoms of a heavily fragmented HDD:

  • Longer load times for files and programs
  • Graphics-heavy apps and games taking too long to load new windows or process new environments
  • Audible noise from the hard drive during system operation

When any of these starts happening consistently, it is probably time to call in the cavalry – by which we mean defragging your computer. So, how to defrag drive which really needs it?

How to Defrag Your Computer

Defragging your PC lets you optimize your hard drive and free up space. However, a good defragmenter will do much more than that. The scattered file chunks need to be placed next to each other to get faster retrieval speeds. Doing this also frees up big chunks of space that new files can be placed in, reducing the chance that they get fragmented very quickly after landing on the hard disk drive. Another aspect of defragmenting is smart file placement, which ensures that the files that the system needs the most are placed in locations that are the fastest and easiest to access.

In short, there are three major aspects of disk defragmentation, which all defragmenters incorporate:

  • File defragmentation. During this process, clusters that contain chunks of a fragmented file are placed next to each other. All the clusters that make up a file are gathered in the same place and ordered consecutively.
  • Space defragmentation. Free space is also defragmented during this process. By this, we mean that the separate clusters of free space are collected into a solid block instead of being scattered around the HDD in smaller separate sections.
  • Smart file placement. Smart file placement during defragmentation means that files are ordered according to the needs of the system. For example, system files can be placed in the outer tracks for faster read-write speeds, thereby improving your PC’s startup time. Smart file placement is dynamic. In general, the most frequently used and important files are placed in the more outer tracks, while the least accessed files are written to the inner tracks of the HDD.

From the foregoing, you should have learned how important disk defragmentation can be to the disk health and overall system performance. If your PC sees a lot of action and starts getting slower due to all the frequent installations and deletions, copying and moving, gaming, and graphics editing, optimizing your hard disk drive with feature-rich defragmentation software will certainly create a noticeable improvement in your system’s overall speed and performance.

You don’t have to take our word for it, though. You can try out a defragmenter yourself and check the results. As pointed out before, an OS like Windows 10 has an inbuilt tool that does the basic things automatically, but you can try out others with better features and a more powerful optimization engine.

Before we bring this guide to a close, there is one more important question to answer: What about solid-state drives?

Can One Defrag an SSD?

SSDs are rapidly replacing HDDs as the storage hardware of choice on modern laptops and desktops alike. Though they remain pricey relative to their mechanical counterparts, there is no denying that the difference in speed between SSDs and HDDs is night and day.

If the sole storage hardware on a PC is an SSD, performing disk defragmentation in hope of improving the drive’s speed is not recommended. In fact, doing so can have the opposite effect.

SSDs, unlike hard disk drives, do not have mechanical moving parts. Thus, reading data on a solid-state drive involves a different process. Since it doesn’t have a mechanical head moving around, fragmentation on an SSD doesn’t cause decreased write speeds, so it doesn’t matter how the file chunks are scattered across the drive. The NAND technology ensures all file components are fetched as soon as they are requested.

Instead of defragmentation, the typical optimization operation on a solid-state drive is the TRIM command, which essentially gives the drive the go-ahead to wipe those blocks of data that have been identified as being no longer in use.

Most inbuilt defragmenters have SSD defragmentation disabled for that reason, as do most third-party tools that do the same thing. However, some of the more feature-rich defragmentation programs out there have an option to defragment an SSD anyway, although we do not recommend taking this step – unless perhaps the drive in question is an SSHD (a hybrid of SSD and HDD technology).

Fed up with your slow PC? Tired of waiting for Windows to start up? Take a look at the most common reasons behind poor performance and the best ways to deal with them here.

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