Magnetic Hard Disk

MAGNETIC HARD DISK

These disks are direct access storage devices. These disks are magnetically coated.

There are two types of disks viz.,

1. Hard disk 2. Floppy disk.

Let us discuss about a Hard disk.

Hard Disk: The hard disk is made of hard aluminium platters. The platter surface is carefully machined until it is flat (or) plane. The platter surface is coated with magnetic material (magnetic oxides). The platter is built into a box. Similar such disks are mounted on a vertical shaft, forming a disk pack and it is shown in Fig. 3.37

This disk pack is placed in a drive mechanism called Hard disk drive. The drive mechanism drives the disk pack with the spindle. The data is written (or) read by the R/W heads in the horizontal sensing arms by moving in and out between the platters with the precaution that the R/W head doesn't touches the surface instead, it fly over the disk surface by a fraction of a millimetre.

Giant magneto resistance (GMR) sensors are used now-a-days as sensing element is hard disk drive.

Advantages

1. It has very large storage capacity.

2. Thousands of files can be permanently stored.

3. Very high speed in reading and writing the informations.

4. This is prevented from dust particles, since they are seated in special chamber.

Disadvantages

1. It is very costly.

2. If data is once corrupted, there is a heavy loss of data.

Note: The hard disk once installed in the system, cannot be removed easily. Latest Hard disk drive using GMR sensor as sensing element is discussed later.