Articles

EasyLink™
A WD utility that allows users to locate and set up a drive as a local drive from any computer quickly and easily.

ECC
Error correction code. A mathematical algorithm that detects and corrects data errors.

ECC on the fly
A hardware correction technique that corrects errors in the read buffer before host transfer and without any performance penalties. These error corrections are invisible to the host system because they do not require assistance from drive firmware.

EESA
Enterprise extensions S.M.A.R.T. accessed. An expanded command set that provides SCSI-like control for server environments, optimizing operation and performance when drives are used in vibration-prone multidrive systems such as rack-mounted servers.

EIDE
Enhanced Integrated Drive Electronics. See PATA

embedded servo control
A design that generates accurate feedback to the head position servo system without requiring a full data surface, because servo control data is stored on every surface (unlike dedicated servo control).

encoding
A process of modifying data patterns before writing them onto a disk surface.

enterprise
Series of computers employed largely in high-volume and multiuser environments such as servers or networking applications; may include single-user workstations required in demanding design, engineering, and audio/video applications.

error log
A record that contains error information.

error rate
The number of errors of a given type that occur when reading a specified number of bits.

ESD
Electrostatic Discharge. Rapid discharge of static electricity that can damage integrated circuits in computers and communications equipment. ESD prevention is aided by such items as ESD wrist straps and ESD hard drive bags.

Ethernet
A standard method of connecting computers to a Local Area Network (LAN) using coaxial cable, twisted pair, and fiber optic wiring standards.

extended partition
A partition on a disk where non-system files (other than DOS or operating system files) can be stored. Multiple partitions can be created on a hard disk: one primary partition and one or more extended partition(s). Operating system files must reside on the primary partition; logical drives can be created on an extended partition.

Data Lifeguard Tools™
A set of software utilities that work in conjunction with embedded Data Lifeguard features to make hard drive installation, drive management diagnostics, and repair simple and worry-free.

Data Lifeguard™
A WD-exclusive data reliability feature that automatically detects, isolates, and repairs problem areas on a hard drive and prevents data loss.

data synchronizer
An electronic circuit that uses a clock signal to synchronize data.

data transfer rate
The rate that digital data transfers from one point to another, expressed in bits per second or bytes per second. Data transfer rate to disk (internal disk transfer rate) is expressed in megabits per second (Mb/s). Data transfer rate from buffer to host (transfer of buffered data) is expressed in megabytes per second (MB/s).

database
A collection of data stored on a computer system medium, such as a hard drive, CD-ROM, etc., that can be used for more than one purpose.

dedicated landing zone
The designated radial zone of a disk, usually at the inner portion, where heads are stored to avoid contact with data cylinders when power to the drive is off.

defect free
A term to describe recording surfaces that have no detectable defects.

defect management
A general method of eliminating data errors on a recording surface by mapping out known media defects. Defective areas are rendered inaccessible, so that subsequent operations write data only to non-defective locations.

desktop
A personal computer sized to fit on or under your desktop. WD internal hard drives are designed to fit into a desktop PC.

DHCP
Dynamic host configuration protocol. A protocol for assigning IP addresses to devices on a network. With dynamic addressing, a device can have a different IP address each time it connects to the network. In some systems, the device’s IP address even changes while it is still connected. DHCP also supports a mix of static and dynamic IP addresses.

differential SCSI
An electrical signal configuration that uses pairs of lines for data transfer, primarily in applications requiring cable lengths up to 82 feet (25 meters).

disk
A rigid platter, usually constructed of aluminum or Mylar® and with a magnetic surface that allows the recording of data.

disk controller
A chip or circuit that controls data transfers between disk and buffer. See also disk drive controller and interface controller.

disk drive controller
Hard disk drive controller electronics, which include the disk controller and interface controller. See also disk controller and interface controller.

disk transfer rate
Speed at which data is transferred to/from disk (platter); a function of the recording frequency. Typical units are bits per second (b/s), or bytes per second (B/s). A hard drive disk transfer rate increases from the inner diameter to the outer diameter of the disk.

distribution channel
Electronics distributors and retail chains that deliver electronic goods to end users through value-added resellers and retail stores.

DLNA
Digital Living Network Alliance. The group of consumer electronics, computing industry, and mobile device companies that sets standards for product compatibility, thus enabling users to share content in their home.

DMA
Digital Media Adapter. A device that gives home entertainment devices the ability to transfer media such as music, photos, and videos to and from other devices over the network.

DMA
Direct memory access. A process that transfers data directly to/from main memory, without passing through a CPU. DMA improves speed and efficiency by allowing a system to continue CPU processing while transferring data to/from a hard drive.

DNS
Domain Name Service. A system that allows a network name server to translate text host names into numeric IP addresses used to uniquely identify any device connected to the Internet.

DOS
Disk Operating System. A 16-bit operating system developed by Microsoft that was formerly the standard operating system for IBM-compatible PCs. DOS does not support multiple users or multitasking.

DPP
Data Path Protection. A feature that prevents possible electronic failures by preventing corruption of data on the hard drive.

DSA
Dual Stage Actuator. DSA is an improvement to the overall capability of the Servo system. It provides a mechanical benefit to improve the response time (higher bandwidth capability) of moving and maintaining the head position over the media.

dual interface
An external storage device with two interfaces available for connection to the computer.

dual-option backup
The ability to back up a drive either manually (on demand) or automatically.

DuraStep Ramp™
WD technology that locks the heads of a data disk to provide additional shock protection.

duty cycle
The time a component, device, or system is actually operating as compared to the time it is powered on; can be expressed as a ratio or percentage.

DVR
Digital video recorder.