A hard disk drive[1] (often shortened as hard disk, hard drive, or HDD) is a non-volatile storage device that stores digitally encoded data on rapidly rotating rigid (i.e. hard) platters with magnetic surfaces. Strictly speaking, "drive" refers to the motorized mechanical aspect that is 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 (except for a filtered vent hole to equalize air pressure) with fixed media.

History of hard disks Edit

HDDs (introduced in 1956 as data storage for an IBM accounting computer)[2] were originally developed for use with general purpose computers. During the 1990s, the need for large-scale, reliable storage, independent of a particular device, led to the introduction of embedded systems such as RAIDs, network attached storage (NAS) systems, and storage area network (SAN) systems that provide efficient and reliable access to large volumes of data. In the 21st century, HDD usage expanded into consumer applications such as camcorders, cellphones (e.g. the Nokia N91), digital audio players, digital video players, digital video recorders, personal digital assistants and video game consoles.

In 1978, NTT's Model 801 introduced a storage capacity of 800 MB per spindle.[3] In 1986, the NTT GEMMY introduced 8.8 GB storage capacity and 4.4 MB/s transfer rate.[4]

In 1990, Toshiba's MK1122FC was the first drive to use a glass hard disk drive platter, replacing the earlier aluminium platters. Glass platters had several advantages, such as greater shock resistance, compared to aluminium platter.[5] In 2005, the first perpendicular magnetic recording (PMR) hard drives were released by Toshiba.[6]

More than 200 companies have produced HDDs historically, though after extensive industry consolidation most current units are manufactured by Hitachi, Seagate, TDK, Toshiba, and Western Digital, as of 2016.

Technology Edit

Buses commonly used for Hard disks Edit

Examples Edit

References Edit

  1. Other terms used to describe hard disk drives include disk drive, disk file, DASD (direct-access storage device), fixed disk, CKD disk and Winchester Disk Drive (after the IBM 3340).
  2. IBM 350 disk storage unit
  3. NTT Model 801 Magnetic Disk Unit (JS4370), Information Processing Society of Japan
  4. NTT GEMMY High-Speed, High-Capacity Magnetic Disk Memory Unit, Information Processing Society of Japan
  5. Toshiba MK1122FC, Information Processing Society of Japan