Hard disk drive

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Hard disk drive

Interior of a hard disk drive
Date invented	24 December 1954[1]
Invented by	An IBM team led by Rey Johnson

Video of an opened hard drive

A hard disk drive (HDD; also hard drive or hard disk)^[2] is a non-volatile, random access digital data storage device. It features rotating rigid platters on a motor-driven spindle within a protective enclosure. Data is magnetically read from and written to the platter by read/write heads that float on a film of air above the platters.
Introduced by IBM in 1956, hard disk drives have decreased in cost and physical size over the years while dramatically increasing in capacity. Hard disk drives have been the dominant device for secondary storage of data in general purpose computers since the early 1960s.^[3] They have maintained this position because advances in their recording density have kept pace with the requirements for secondary storage.^[3] Today's HDDs operate on high-speed serial interfaces; i.e., serial ATA (SATA) or serial attached SCSI (SAS).

Contents

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• 1 History
• 2 Technology
  • 2.1 Magnetic recording
  • 2.2 Components
  • 2.3 Error handling
  • 2.4 Future development
• 3 Capacity
  • 3.1 Units of measuring capacity
  • 3.2 HDD formatting
  • 3.3 Redundancy
  • 3.4 HDD parameters to calculate capacity
• 4 Form factors
  • 4.1 Current hard disk form factors
  • 4.2 Obsolete hard disk form factors
• 5 Performance characteristics
  • 5.1 Access time
    • 5.1.1 Interleave
    • 5.1.2 Seek time
    • 5.1.3 Rotational latency
    • 5.1.4 Data transfer rate
  • 5.2 Power consumption
    • 5.2.1 Power management
  • 5.3 Audible noise
  • 5.4 Shock resistance
• 6 Access and interfaces
  • 6.1 Disk interface families used in personal computers
• 7 Integrity
  • 7.1 Actuation of moving arm
  • 7.2 Landing zones and load/unload technology
    • 7.2.1 Landing zones
    • 7.2.2 Unloading
  • 7.3 Failures and metrics
• 8 External removable drives
• 9 Market segments
• 10 Sales
• 11 Icons
• 12 Manufacturers
• 13 See also
• 14 Notes and references
• 15 Further reading
• 16 External links