It is designed to solve a problem that occurs because of the way hard disks store data. Hard disks store data in chunks called sectors . 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 processor and its memory, the time it takes for the arm to move and for a sector to spin into place is an eon. See How Hard Disks Work for more information. So let's imagine that you install a new application onto an empty hard disk. Because the disk is empty, the computer can store the files of the application into sequential sectors on sequential rings. This is an efficient way to place data on a hard disk.