A Buyer's Guide to Understanding and Evaluating Optical Storage - Glossary Of Terms (Continued)

Mission-critical data

Data or information considered to be so important that its loss would have grave consequences for all or part of a business. For example: customer account information at a bank, or patient information at a hospital.


The combination of several media formats used for the delivery of information. Many commercial CD-ROMs use a multimedia format, combining text, photos, audio, animation and video on a single disk.

Near-field recording

An optical disk storage technology that combines elements of hard disk and magneto-optical (MO) storage. Though still under development, the technology is expected to deliver hard disk-like performance with greater storage capacities and lower storage costs than current technologies.

Near-online storage

A cross between online and offline storage, usually consisting of data stored in optical jukeboxes. Near-online storage is less expensive, more durable, and takes only slightly longer to access than online storage kept on high-speed hard disks. It is significantly faster and easier to access than offline storage.


The ability to interconnect a number of PCs, workstations, servers and peripherals for the purpose of sharing, sending, receiving and managing information, files, e-mail and other data.

Offline storage

Infrequently accessed data that is stored offline in a tape archive or file cabinet. Offline storage is the least expensive and slowest storage method, consisting primarily of tape, microfiche and paper media. Restoring offline data to an online environment must be handled manually.

One big disk

A seamless, transparent combination of hard disks, optical jukeboxes, and other storage technologies integrated into a single system. The net effect for data users is a virtually infinite storage solution that looks like one big disk, but is, in reality, a mixture of online and near-online storage.

Online storage

The fastest and most expensive storage alternative, consisting of frequently accessed files found on a computer's hard disk.

Operating system

Software instructions that tell a computer how to operate. For example: MS-DOS, Windows 95, Windows NT, and HP-UX.

Optical disk

A storage medium that generally uses a laser to write and read data. See WORM, CD-ROM, CD-R and CD-RW.

Optical storage

A storage alternative to hard disks that provides random-access capability like hard disks. Compared to hard disk storage, optical storage offers lower cost, higher capacity, higher reliability and a higher degree of removability and transportability. However, optical disk access times are slower than hard disks, due primarily to the weight of the optical head that reads and writes data. Most optical storage technologies use a read/write laser to store data: to write, the laser heats the recording surface of the media, causing a physical change that is detected during reads.

Optical Storage Technology Association (OSTA)

An international trade association founded in 1992 to promote the use of writable optical technologies and products.

Peer-to-peer architecture

A network of two or more computers using the same programs or types of programs to communicate and share data.

Phase-Change technology

An optical disk storage technology that uses a plastic disk and metal recording layer to store data. Heat generated by the drive's laser changes the molecular structure of the metal, transforming it from an amorphous to highly reflective crystalline state. The changes in reflectivity are detected during reads. Used for CD-RW and DVD rewritable.


The ability to plug devices into a computer and begin using them immediately, without having to install special drivers.


The ability to move storage media from one point to another. Tapes and optical disks are highly portable since they can be easily moved from a working environment to a different location for storage.

Primary storage

Online storage of electronic data, typically found on a computer's hard disk. This includes frequently used data, work in process, or data that is not frequently used but must be immediately available at all times.


Quarter-inch cartridge (pronounced "Quick"), this recording technology uses a mini-cartridge for tape storage. There are many QIC standards, each defining a method for reading and writing data to tapes.

Random access

The ability to skip randomly from track to track on a storage medium. Optical disks, magnetic hard disks and audio CDs allow random access to data tracks. Audio tapes, by comparison, allow only sequential access (i.e. fast-forward or reverse) to locate stored data.


The act of copying files or data from a backup storage device to their normal location on a computer's hard disk, often to replace files or data that were accidentally lost or deleted.


A machine that can sense and react to input, and cause changes in its surroundings with some degree of intelligence, ideally with no human supervision.


The "guts" of an optical jukebox, usually consisting of a mechanical arm that automatically transports optical disks inside the jukebox cabinet.

Seek time

The time it takes for the read/write head on a disk or tape drive to find a specific track.


A computer that provides access to a network and its resources, runs administrative software controls, and provides services (such as file storage and retrieval) for desktop computers.


A physical location inside an optical jukebox, where optical cartridges reside when not being used by an optical drive.

Small Computer System Interface (SCSI)

An industry standard for connecting peripherals such as printers, scanners, optical drives and tape drives to a microprocessor. SCSI covers both hardware and software standards for allowing computers and peripherals to communicate with each other.

Storage capacity

The maximum amount of data that can be stored on a given medium.


A software utility for tape storage systems. It warns users when there is a backup problem, and tells administrators when maintenance is recommended or required.


A software utility for tape storage systems. It assists users and administrators during hardware installation, and provides assurance that an installation has been completed fully and correctly.

Terabyte (TB)

A unit of measurement for high-capacity data storage. One terabyte equals approximately one trillion bytes, or 1000 gigabytes, of information.


A performance measurement indicating the volume and speed of data as it flows from one point to another through a data pipeline. High throughput indicates a system architecture that can carry high volumes of data at high speeds, resulting in high system performance.

Transfer rate

The rate of speed at which data travels through a bus or device, typically measured in bits, bytes, kilobytes or megabytes per second.


A mini-cartridge tape technology that supports QIC tapes. Travan cartridges contain approximately twice the amount of tape as QIC cartridges. Travan products can read QIC tapes.


In imaging, a software program that queues, tracks and manages documents and collections of documents as they progress from entry into the system, through the various departments in the organization, to their final destination.


Write Once, Read Many. An optical storage technology that allows disks to be written just once but read without limit. WORM drives write directly to an optical disk from a host computer. Both the drives and disks include built-in safeguards to assure that data, once written, cannot be erased, overwritten or altered.

Write protect

The use of various safeguards to prevent a computer system from overwriting a storage medium. Floppy disks have a sliding tab for "physical" write protect. Hard disks support "logical" write protect in software. Optical disks often use a combination of physical and logical write protect safeguards.

Francis Bacon