Defragmentation

December 2016

What is fragmentation?

When you save a file on a disk (which is initially empty), all the information concerning this file is written sequentially, one piece after the other. When you save a second file, it will be written after the first, and so on.

Before fragmentation

However, when a file is deleted, this creates a blank space on the disk. Now, the following files will fill up the "holes", and will be scattered in pieces over the disk. This phenomenon is even more pronounced on a hard drive, which has a large capacity and contains a huge number of files.

After fragmentation

So, when the system accesses a file, the disk head will need to visit all the locations where the file pieces are saved to read them. This will result in reduced performance...

How can you remedy this fragmentation?

Copying, moving and deleting files is inevitable, as the system is constantly writing temporary files. So you need to use a defragmentation tool, which is a software package that is able to reorganize the files on the hard drive so that the file "pieces" are stored contiguously so as to form more "compact" files.

It is recommended that you regularly (around once a month) use a defragmentation utility that will reorganize the data stored on the disk.

Some defragmentation tips

The defragmentation tool uses algorithms to re-order the files on the disk in the best possible manner. The file fragments scattered over the disk are moved, one by one, to free disk space (not used by files) on a temporary basis, and are then relocated to an appropriate place. The more free disk space there is available, the easier the defragmentation will be.

Furthermore, if the data is changed during defragmentation, the tool has to recalculate how to move the files to take into account these new changes. It is therefore essential to close all open applications before starting the defragmentation. Now, the operating system has processes that are running in the background and accessing the hard drive (especially if the amount of RAM on the system is insufficient, as the system creates swap files).

Therefore, it is strongly recommended, if your computer is running Windows, that you reboot in safe mode, which is a mode in which a minimal configuration is loaded. To reboot the computer in safe mode, you need to press the F8 key just after the computer starts up (RAM test and disk detection) and just before the message Starting Windows.


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