8. Fragmentation and De-fragging

Because of the way the file manager works, the continual saving and deleting of files on a hard disk will cause the files to fragment all over the hard disk.

Now a hard disk has to physically move its read-write heads in order to retrieve or write to a file. And the more scattered or fragmented the files become then the harder a hard disk has to work and the slower it becomes to retrieve them.

A badly fragmented hard disk will appear to be significantly slower than a 'clean' one.

So system tools have been developed that will de-fragment a hard disk. They will steadily work out how to shuffle the data around so a file will have contiguous clusters, thus being accessed more quickly.

A good de-fragmenting tool will also work out which are the most used files and try and locate them towards the centre of the disk where disk sectors are whizzing faster below the read-write heads.

It is a lengthy job though, de-fragmenting a disk could take many hours and so it is a job best left for a quiet period such as over night.