Hard disk drive

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Hard disk drive
An IBM hard disk drive with the metal cover removed. The platters are highly reflective.
Date Invented:	September 13, 1956
Invented By:	Reynold Johnson
Connects to: Controller (typically on motherboard) via one of PATA (IDE) interface SCSI interface SATA interface SAS interface Controller (typically found on servers) via one of FCAL interface SCSI interface Controller (formerly common, now disused) via one of ESDI interface ST-506 interface
Market Segments: Desktop Mobile Enterprise Consumer Other/Miscellaneous

A hard disk drive (HDD), commonly referred to as a hard drive or hard disk,^[1] is a non-volatile storage device which stores digitally encoded data on rapidly rotating platters with magnetic surfaces. Strictly speaking, "drive" refers to a device distinct from its medium, such as a tape drive and its tape, or a floppy disk drive and its floppy disk. Early HDDs had removable media; however, an HDD today is typically a sealed unit with fixed media.^[2]

HDDs were originally developed for use with computers. In the 21st century, applications for HDDs have expanded beyond computers to include digital video recorders, digital audio players, personal digital assistants, digital cameras, and video game consoles. In 2005 the first mobile phones to include HDDs were introduced by Samsung and Nokia. The need for large-scale, reliable storage, independent of a particular device, led to the introduction of configurations such as RAID arrays, network attached storage (NAS) systems and storage area network (SAN) systems that provide efficient and reliable access to large volumes of data.