Partition
A division of a disk/disc. Normally there is one partition per disk/disc side, but if necessary more can be defined.

Purge
The action of removing a clean file from the file cache, to create space.

no entry

Rock Ridge or Rock Ridge Interchange Protocol
An extension to ISO9660 which allows additional information to be stored in the file system, allowing UNIX like file names and attributes to be stored. If a disc uses Rock Ridge, a system which understands Rock Ridge will use the additional information present, and a system which does not (e.g. MS-DOS) will only use the standard ISO9660 information.

RS232
A serial interface. RS232 interfaces are used to control the robotics on some libraries.

SCSI (Small Computer Systems Interface)
The usual interface between the disk/disc, robotics devices and the host computer. SCSI can be used for attaching different types of device (e.g. hard disk drives, tape drives, CD/DVD-ROMs or scanners) to a computer.

A well established standard interface that is used to connect high performance peripherals to a computer. Each piece of hardware has its own target identifier on the bus. There are several different types of SCSI buses with different properties and using different connectors.

SCSI Bus
The actual connection shared between the various SCSI devices attached to the computer.

Sector
The smallest addressable unit on an optical disc or CD-ROM. Optical discs usually have sector sizes of 512 or 1024 or 2048 or 4096 bytes; CDs and DVDs have one of 2048 bytes (although some CD-ROM drives have modified firmware to allow them to behave as though they have a 512 byte sector size).

Session
A unit of recording on a CD. A session consists of 1 or more tracks which are viewed as an integrated whole. The tracks making up a session are usually (but not necessarily) all recorded at the same time, but separate sessions can be recorded on the disc as required by the user.

Single-session
A disc which contains a single session. Also used to refer to a CD-ROM player which can only read single-session discs.

Subsystem
A unit of storage within an XFS. A subsystem contains an integral file system, and can be added or removed from an XFS. It occupies a disc partition, and there is usually a single subsystem per single sided disc, or two for a double sided disc.