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Data Recovery Glossary (Letter D)

January 18th, 2010

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.

Data Recovery
Data recovery is the procedure used to recover data from a variety of media and operating systems that has been lost by either hardware failure, human error, software bugs, a virus or a natural disaster.

Data Synchronizer
An electronic circuit that uses a clock signal to synchronize data to facilitate interpretation.

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: The internal disk transfer rate in Mbits per second.Data Transfer Rate from the Buffer to the Host: Based on the transfer of buffered data in MB per second.

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

Defect Free
A term used to describe recording surfaces that have no detectable defects.

Defect Management
A general methodology of eliminating data errors on a recording surface by mapping out known defects on the media. The defective areas are rendered inaccessible, so that when information is written to the disk, it is stored to non-defective locations on the disk.

Differential SCSI
An electrical signal configuration which uses pairs of lines for data transfer. Used primarily in applications requiring long cable lengths of up to 82 feet (25 meters).

Direct Memory Access (DMA)
A process for transferring data directly to and from main memory, without passing through the CPU. DMA improves speed and efficiency by allowing the system to continue CPU processing even while it is transferring data to/from the hard drive.

Directory
A list of file names and locations of files on a disk.

Disk
A rigid platter, usually constructed of aluminum or mylar, with a magnetic surface that allows the recording of data, that is stored inside the drive.

Disk
A portion of a computer’s RAM set aside for temporarily holding information that has been read from a disk. The disk cache does not hold entire files as does a RAM disk, but information that has either been recently requested from a disk or has previously been written to a disk.

Disk Controller
The chip or circuit that controls the transfer of data between the disk and buffer. (See also disk drive controller and interface controller).

Disk Drive
The motor that actually rotates the disk, plus the read/write heads and mechanisms.

Disk Drive Controller
The hard disk drive controller electronics which include the disk controller and the interface controller. (See also disk controller and interface controller.)

Disk Operating System (DOS)
The computer program that controls the organization of data, files and processes on the computer.

Disk Transfer Rate
Speed at which data transfers to and from the disk media (actual disk platter); a function of the recording frequency. Typical units are bits per second (BPS), or bytes per second. Hard drives have an increasing range of disk transfer rates from the inner diameter to the outer diameter of the disk.

Distribution Channel
Electronics distributors and certain retail chains that deliver electronic goods to end users through value-added resellers and some retail stores.

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