what is defragmentation: Explained: What is disk defragmentation and why it is beneficial – Times of India

When you save a file onto your PC, you can see it at one point on the screen and can double click on it to open it or right click to access other options too. It looks like that the saved file, like a Word document or a video file, is there at a certain location in totality and since you can see that file on your screen, you might think that all of the parts of the file are at one place physically in your hard disk. It appears so, yeah, but it may not be true.
There might be ‘fragments’ or the individual pieces of that file scattered throughout various memory locations in your hard disk drive, and this happening is called fragmentation. In the same way, the process that reverses it is called defragmentation because in the end, you want all the parts of the file sitting closely to each other as one, right? So that your hard disk does not have to read from multiple locations and you can access it without causing any delay.
An analogy would be a toy which can only be made from different blocks. Now, suppose a kid misplaces a few pieces of the toy in the house. They are there in the house but if the kid has to play, the parents will have to spend some amount of time to retrieve them. Once all the blocks are accounted for, the toy can be built fully. Another analogy could be a deck of cards, a few cards of which get misplaced at home. To play the game, you need all of them in one place. Which is what defragmentation does. Think of defragmentation as organising any component of your life. If you are an organised person, things move smoothly and you don’t lose time.
Similarly, when it comes to retrieving a fragmented file, your hard drive has to spend more time getting the fragments of the file together. It loses time. So, fragmentation will occur when data isn’t written in a way that all its components are placed very close to each other physically on the drive. Defragmentation makes those components come together, so that they sit close to each other, so that the next time you try to access that file, the drive responds faster.
The cause of fragmentation and the remedy
Fragmentation is mostly caused when gaps develop between the different parts of a file as the system has to store them in different locations. Suppose you deleted a file. Now that leaves a space in the memory which is often small to accommodate the whole of a new file being saved. So, the system will try to fit in whatever portion of the new file it can in the space and shift the other parts to the other location in the hard disk.
There is no way of predicting how a user is going to save files on his/her system, so there are high chances of fragmentation happening somewhere along the line. But if there is too much unorganised space in the memory, you might experience the PC becoming slow. Hence, there is Microsoft’s own Disk Defragmenter tool for Windows users. There are other third party tools also available which will do the defragging.
If your system or drive component is showing signs of sluggishness, defragging it might fix it. If there are plenty of mismanaged fragments sitting inside the drive, it may take a bit of time for the process to get complete. Just don’t start defragging your hard drive every now and then. Once in a while should be good enough.
https://www.lifewire.com/what-is-fragmentation-defragmentation-2625884