Hard Disk Drive is a magnetic storage medium of computer, on which data is written on the surface of a rotating disk. So in this article we will go through Overview, Structure and Function of a Hard Disk Drive. Hard Disk Drive can be external, which can be used as a movable storage device and Internal Hard Disk Drive is designed for usage on desktop computers and Servers. There are methods and gadgets available to make an Internal Hard Disk Drive to use as External – we wrote in details about Disk Enclosures before.

Overview of Hard Disk Drive

A Hard Disk Drive has a magnetic material coated plates where the information to be recorded. In contrast to sequentially addressable storage media such as magnetic tape or punched tape drives, Hard Disk Drive is a direct access storage device or DASD, as data can be accessed directly from a Hard Disk Drive.

Recently, with comparable storage capacity and flash memory, called Solid State Drives (SSDs) and hybrid ones are available. SSDs are still priced higher than any currently available Hard Disk Drive.

Structure  of Hard Disk Drive

Common form factors for Hard Disk Drive (the width) is 5.25 “, 3.5″, 2.5 “and 1.8″ . Upto 0.85 inch Hard Disk Drive is available but usually 3.5 inch hard drive is the standard in desktop computers. A hard disk consists of one or more rotating mounted disks, one axis, also called spindle, an electric motor to rotate the disks, moving heads which read and writes the data, an IC for for controlling the motor and head, a dedicated RAM, outer very strong casing and the interfaces to attach for power supply and data exchange.

The discs consist mostly of treated aluminum – alloy steel. They are quite hard and resistant to a minute physical insult at top rotating speed of 5400-10000 min -1. The case of a hard disk is very strong, mostly it is made from an aluminum alloy and fastened with proprietary repeats (not screws). This makes sure the fact – if the casing of Hard Disk Drive is opened – it will be obvious from the marks left by the instruments on the body of Hard Disk Drive casing for opening it.

Function of Hard Disk Drive

The capacity of hard disk drive is measured in megabytes (1 MB = 1,000,000 bytes), gigabytes (1 GB = 1,000,000,000 bytes) or terabytes (1 TB = 1,000,000,000,000 bytes). The primary usage of a Hard Disk Drive is to install the Operating System (like Windows, Mac, Linux) and save the data on it. Hard Disk Drives are also used for backup purpose or for archival purpose as the cost of per MB unit is still much lower for a Hard Disk Drive than an optical disk.