How does disk defrag work?
The word “disk defrag” is typically used to refer to the Microsoft Windows utility called Disk Defragmenter. It is designed to solve a problem that occurs because of the way hard disks store data. If you have read the article How Hard Disks Work, then you know three key facts about hard disks: • Hard disks store data in chunks called sectors. If you imagine the surface of the disk divided into rings (like the rings of a tree), and then imagine dividing each ring into pie-slices, a sector is one pie-slice on one ring. Each sector holds a fixed amount of data, like 512 bytes. • The hard disk has a small arm that can move from ring to ring on the surface of the disk. To reach a particular sector, the hard disk moves the arm to the right ring and waits for the sector to spin into position. • Hard disks are slow in computer terms. Compared to the speed of the
