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Glossary of Hard Disk Drive Terminology (Letter H)

January 9th, 2009

Half-Duplex
A communications protocol that permits transmission in both directions but in only one direction at a time.

Half-height Drives
Standard 3.5-inch hard drives are available in heights of 1.0-inch and 1.6-inches. Half-height drives measure 1.6-inches in height.

Hard Drive
An electromechanical device used for information storage and retrieval, incorporating one or more rotating disks on which data is recorded, stored and read magnetically. Western Digital’s principal product.

Hard Drive Industry
The combined manufacturers of hard drives. In the United States, the industry is led by IBM, Maxtor, Seagate, Quantum and Western Digital.

Hard Error
An error that is repeatable every time the same area on a disk is accessed.

Hard Sectored
A technique that uses a digital signal to indicate the beginning of a sector on a track.

Head
The minute electromagnetic coil and metal pole which write and read back magnetic patterns on the disk. Also known as a read/write head. A drive with several disk surfaces or platters will have a separate head for each data surface. See also MR Head.

Head Actuator
A motor that moves the head stack assembly in a hard drive to align read/write heads with magnetic tracks on the disks.

Head Crash
Refers to the damage incurred to a read/write head when the head comes into contact with the disk surface. A head crash might be caused by severe shock, dust, fingerprints, or smoke, and can cause damage to the surface of the disk and/or the head.

Head Disk Assembly (HDA)
The mechanical components of a hard drive, including the disks, heads, spindle motor and actuator.

Head Loading Zone
An area on the disk specifically reserved for the heads to use when taking off or landing when power to the drive is turned on or off. No data storage occurs in the head loading zone.

Head Stack Assembly
The electromechanical mechanism containing read/write heads and their supporting devices.

Headerless Format
The lack of a header or ID fields (track format). This enables greater format efficiency and increased user capacity.

High-end Market
The enterprise market.

High-Level Format
A high-level format must be performed (with EZ-Drive or the Format command) on your new Western Digital hard drive before you can use it. Formatting erases all the information on a hard drive and it sets up the file system needed for storing and retrieving files.

Host
The computer that other computers and peripherals connect to. See also initiator.

Host Adapter
A plug-in board that acts as the interface between a computer system bus and the disk drive.

Host Interface
The point at which the host and the drive are connected to each other.

Host Transfer Rate
Speed at which the host computer can transfer data across the SCSI interface; or, the speed at which the host computer can transfer data across the EIDE interface. Processor Input/Output (PIO) modes and Direct Memory Access (DMA) modes are defined in the ATA-4 industry specifications for the EIDE interface.

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