D

daemon

A program that runs automatically and in the background. Daemons often provide valuable services such as automated file transfers and establishing network connections.

device

Another term for a hardware component in a computer.

device alias

An ordinary name for a configured hardware device, used for human convenience.

device driver

A small software program that enables a hardware device to communicate with the operating system.

device tree

A hierarchical list of all configured devices in the computer.

direct map

An automount point that contains a direct association between a mount point on a client and a directory on a server.

Directory Information Tree (DIT)

The hierarchical database that stores information on a Lightweight Directory Access Protocol (LDAP) server.

dirty regions

Areas of a mirrored volume that are out of synchronization with the other submirror or submirrors.

disk controller

A hardware device built into the hard disk or motherboard that controls hard disk behavior.

disk heads

Also known as read/write heads, disk heads are responsible for reading and writing information on hard disks.

disk label

The first sector of the hard disk, which contains disk geometry information as well as partition information. The disk label is also called the Volume Table of Contents (VTOC).

disk mirroring

The process of using two or three submirrors (different hard disks) to hold identical copies of data. Disk mirroring is used as a form of online fault tolerance.

disk platters

Magnetically coated plates located within a hard disk. Data is stored on the disk platters.

disk set

Also known as a shared disk set, it's a logical grouping of hard disk slices that can be shared by multiple hosts.

disk slice

A range of continuous sectors located on a hard disk, logically defined as one unit. Disk slices are also often called partitions.

disk striping

A process in which data is written evenly across hard disks or slices. Also called RAID 0, disk striping is done to improve overall disk read and write performance.

disk striping with parity

A process in which data is written evenly across hard disks or slices, and a parity (backup) block is also written. Also called RAID 5, disk striping with parity provides online fault tolerance as well as some overall increase in disk read and write performance.

distributed file system

Also known as a network file system, a distributed file system is one that is accessed across a network connection.

Domain Name Service (DNS)

A service that resolves host names to IP addresses. DNS replaces the need for local hosts files and is the name resolution method used on the Internet.

dynamic reconfiguration

The automatic configuring or disabling of a device added to or removed from the computer while the computer is running.