Information:

Storage Glossary

Access Right - The operation of reading, writing or updating information on some storage medium, such as a disk.

AD - Active Directory.

Agent - Software that runs on the client that enables the client to be managed. Also called management agent.

Appliance - A server or other computer that is designed for a highly specialized, dedicated use, such as Web hosting or Web storage. Appliances are often low-cost and easy to implement.

Application Server - A server that runs between clients and back-end business applications and databases. It handles application logic, determining how the business system should behave. Also called an appserver.

Arbitrated loop - A Fiber Channel configuration that attaches multiple communicating ports in a loop. Two or more ports can interconnect, but only two ports can communicate simultaneously.

Array - A collection of two or more disk drives.

Asynchronous Transfer Mode (ATM) - A switched network transmission technology that is highly scalable and provides typical speeds of up to 644 MBps. ATM services are highly reliable, and commonly include Quality of Service (QoS) guarantees. See also frame relay, dedicated leased line.

ATA/IDE - An Advanced Technology interface designed for PC-compatible computers. Also known as Integrated Drive Electronics (IDE).

Availability - The amount of time that information stored on a computer system or network is accessible.

Backup - A copy of a file, directory, or volume on a separate storage device from the original, for the purpose of retrieval in case the original becomes lost or inaccessible.

Bandwidth - The amount of data that can be transferred through an interface in a given period of time.

Bus - A transmission channel through which electrical signals are carried from one chip to another chip.

Byte - An eight-bit organizational unit for data.

Cable Modem Service - A service that delivers high-speed Internet access to businesses and consumers over cable lines. A separate cable modem or router is usually required to use the service. See also DSL, ISDN, frame relay, dedicated leased line, T1/T3.

Cache/Caching - A technique of temporarily storing frequently accessed data in random access memory (RAM) or in a special area of a hard disk drive, to reduce the time required to read and write data.

Category 5 Cable (Cat 5) - The wire most commonly used in Ethernet LANs. It connects computers and devices to an Ethernet network. See also twisted pair.

Central Processing Unit (CPU) - The part of a computer that includes the circuits that interpret and execute instructions. The CPU, or microprocessor, is the "brain" of the computer.

CIFS - Common Internet file system. Used for client/server communication within Microsoft operating systems.

Client - A computer system that requests access to the data, services or resources of a server (another computer system). Multiple clients may share access to a common server.

Client/Server Network - A network set-up in which one or more computers -- the clients -- make service requests from a computer called the server, which fulfills them. Most business applications written today are designed for the client/server network model. See also peer-to-peer network.

Clustering - A technique in which two or more servers are interconnected and can access a common storage pool. Clustering prevents the failure of a single file server from denying access to data and adds computing power to the network for large numbers of users.

Coaxial Cable - A cable consisting of one conductor, usually a small copper wire, within and insulated from another conductor of larger diameter, usually copper tubing or copper braid.

Communication Server - The hardware and software that handles user requests to access a network remotely. Also called a remote access server. Also called a remote access server.

Connectivity - The method by which hardware devices or software communicate with other hardware or software.

Controller - The unit that translates computer data and commands into a form suitable for use by the storage disks.

Copy-on-write for hot backup - The process of copying old data blocks on disk to a temporary disk location when files are being updated, or a database object is being backed up.

DAS - Direct attached storage.

Data mining - The process of analyzing data to identify patterns or relationships.

Data Warehouse - An aggregate of information from various resources stored centrally to provide flexible and efficient access to data. Many organizations keep a data warehouse to maintain large amounts of business data, such as transaction histories, and analyze it to help support business decisions.

Database Server - A server on a LAN that is dedicated to storing and retrieving information from databases.

Dedicated Leased Line - A data channel that permanently connects two or more locations that is always kept on. Dedicated leased lines are commonly used for connecting geographically distant businesses and for accessing the Internet because they support fast and secure data transfer. See also cable modem service, DSL, ISDN, frame relay, T1/T3.

Dense Wave Division Multiplexing (DWDM) - Breaks down laser light in a fiber into a number of different wavelengths up to 40. Each wavelength is a separate circuit. Each circuit operates at very high speeds, making the total aggregate capacity unfeasibly massive.

Digital Subscriber Line (DSL) - A technology that delivers high-speed Internet access to businesses and consumers over ordinary copper telephone line. A separate DSL modem or router is usually required to use the service. See also cable modem service, ISDN, T1/T3, dedicated leased line, frame relay.

Duplexing - The process of duplicating information from one set of drives to another so that an exact copy of the data always exists. Similar to mirroring. See also RAID.

Dynamic Host Configuration Protocol - A protocol for assigning dynamic IP addresses to devices on a network. DHCP supports a mix of static and dynamic IP addresses.

E-business - A business approach in which some or all of the sales and customer support processes are managed electronically, usually via the Internet.

e-mail Server - A server that manages e-mail communications. An e-mail server accepts and manages incoming mail, and stores and forwards outgoing mail.

Enterprise Management - Management of the total heterogeneous network.

Ethernet - The most widely used local area networking (LAN) technology, also referred to as 10/100 Ethernet. Ethernet transmits information between computers at speeds of 10 and 100 Mbps.

Extranet - A private network that uses Internet infrastructure to connect a business securely with outside customers and business partners. Firewalls and encryption technology "privatize" a slice of the public network to allow companies to exchange data confidentially.

Fabric - The interconnection of two or more Fiber Channel switches in such a manner that data can be physically transmitted between any of the switches.

Failover - In the event of a component failure, its function is automatically assumed by a redundant component.

Fault tolerance - The ability of a system component to fail without causing the entire system to shut down. A fault tolerant system requires redundancy in disk drives, power supplies, adapters, controllers and cabling.

FDDI - Fiber distributed data interface. An American National Standards Institute (ANSI) standard token passing network that uses optical fiber cabling and that transmits at 100 Mbps up to two kilometers.

Fiber Channel - A technology that is capable of transferring data between computer devices at a rate of up to 1 Gbps, or one billion bits per second. Fiber Channel supports point-to-point, switched, and loop topologies.

File Server - A server that stores programs and data files shared by users on a network.

Firewall - A set of security tools designed to separate an internal network from the public Internet in order to keep unauthorized users out of a restricted network. Firewalls are the primary line of security defense for businesses.

Firewire (IEEE 1394) - A high-speed serial-bus standard that offers enhanced connectivity and data transfer for video, audio and storage peripheral applications through a universal input/output (I/O) interface.

Form Factor - The size, shape and configuration of a computer hardware object. The term is often used to describe the size of a computer case or chassis. It can also be applied to internal components such as disk drives and circuit boards.

Frame Relay - A transmission technology used to connect two networks or provide Internet access at speeds from 56 Kbps (typical analog modem speed) up to 44.6 Mbps. Frame relay uses T1, T3 or other digital leased lines for access, but unlike typical dedicated leased lines, it can portion varying amounts of bandwidth as needed by the network. See also cable modem service, ISDN, T1/T3, DSL, dedicated leased lines.

FreeBSD - FreeBSD is an advanced BSD UNIX operating system for the Intel compatible (x86), DEC Alpha, and PC-98 architectures.

FTP - An application layer protocol that uses Transmission Control Protocol (TCP) and telnet services to transfer bulk-data files between machines or hosts.

Gigabit (Gb) - One billion bits.

Gigabit Ethernet - A networking technology in which data is transmitted at one gigabit per second. The new Gigabit Ethernet interface is over standard copper cable (CAT 5) and is an IEEE 802.3u standard. The interface also supports automatic speed selection between 10, 100 and 1000 Mbps.

Gigabyte (GB) - One billion bytes or 1,024 megabytes.

Graphical Console Direction - The ability to control a server remotely using a graphical operating environment from an alternate location. Works with Microsoft Windows 2000 and Windows NT.

GUI - Graphical user interface.

HDD - High density drives.

Host bus adapter (HBA) - An adapter that plugs into a host and lets the host communicate with a SCSI device.

Hot spare - A RAID storage feature that allows a spare drive to be configured online for automatic reconstruction in the event of a disk failure.

Hot swappable - The ability to replace a defective component while the system continues to function normally.

HPNA 2.0 - Home phone-line networking architecture 2.0 uses a standard telephone cable and RJ11 connector for networking with a transfer rate of 10 Mbps.

HSM - Hierarchical storage management.

HTTP (Hypertext Transfer Protocol) - The means by which a Web browser and a server delivering Web pages communicate.

Hub - A device used to create a small-scale network by providing a common connection to all devices on the network.

IDE - Integrated Drive Electronics. A type of hard disk drive also known as ATA.

IFCP - Extended SAN tunneling standard.

In Band - The state of a server when it is operational.

InfiniBand - Derived from "infinite bandwidth." A switched-fabric I/O technology that ties together servers, storage devices and network devices, easing the bottlenecks created by data-intensive files such as streaming video, voice and audio.

Interface - A shared boundary between external connections that links differing systems, programs or devices. It allows these connections to work together and exchange information.

Integrated Services Digital Network (ISDN) - A communications technology that enables digital transmission over ordinary telephone lines. Typical ISDN Internet access operates at 128 Kbps, slower than comparable DSL or cable modem service. See also cable modem service, DSL, T1/T3, dedicated lea sed line, frame relay.

IP - Internet Protocol - One of many components that make networks work. Its current popularity is largely due to the success of the Internet. It provides a standardized addressing system and packaging system for data. Analogous to the standard postal addresses and standard envelops in the postal systems around the world. Clearly a postal system needs many more things to make it work it's the same for IP. Don't get caught out by folks that tell you about "IP networks." Networks have IP in them, but IP does not make a network.

Internet Service Provider (ISP) - A company that provides businesses and individuals with access to the Internet for Web browsing and e-mail. Many ISPs also offer Web site hosting services. Users of ISP services can connect to the Internet via a dial-up modem or through broadband connections such as cable modem service, DSL or T1/T3 lines.

Intranet - An private network that allows user in a company to access data using a Web browser. It looks like a World Wide Web site but is strictly internal and doesn't actually connect to the Internet.

Interoperability - The ability of computer systems made by different manufacturers to operate with one another.

I/O - Input/output.

IPSec - The new Internet Protocol Security specification.

iSCSI - The iSCSI protocol takes advantage of the investment in existing IP networks to facilitate and extend SANs.

JBOD - Just a bunch of disks. An array without a controller.

Kernel - The core of an operating system. It performs basic functions such as allocating hardware resources and managing memory.

Keyboard, Video and Mouse Capability (KVM) - KVM is essential in confined computer areas where having a separate monitor, keyboard, and mouse dedicated to each server is impractical. It allows you to configure and manage the server using the keyboard, monitor and mouse of another computer.

Kilobyte (KB) - A unit of measure equaling 1,000 bytes.

Knowledge Management - The management of a company's in-house knowledge base to facilitate data mining and effective information sharing throughout the organization.

LAN - Local area network. A network of computers that are separated by a short distance and generally connected to a single, shared server.

Latency - The amount of lag time that results when data is moved from one designated point to another. The term is used to refer to a delay in response when moving data in a network or single computer system. In general, the more traffic your network gets, the greater the latency will be.

LES Circuits - LAN Extension Service circuits. Fiber Optic tails for delivery of Ethernet from our PoPs to the customer's network.

Linux - A Unix-based computer operating system whose kernel was developed by Linus Torvalds. Linux is an open-source software, See also Windows NT/2000, Netware, Network Operating System, UNIX.

Load balancing - The even allocation of application I/O or computational demands across a system's physical resources in order to serve users more efficiently.

LUN - Logical unit number. Used to identify SCSI devices so the host can address and access the data on each disk drive in an array.

MAC - Media access control address for Ethernet device address.

MAN - Short for Metropolitan Area Network, it's a network that covers a metropolitan area such as London, Manchester or Birmingham i.e. bigger than a LAN but smaller than a WAN and usually taking advantage of cheaper connectivity charges available in these areas to provide higher bandwidth.

Mbps - Megabits per second.

Megabyte (MB) - A unit of measure consisting of one million bytes or 1,000 kilobytes.

MIB - Management information block. Part of the SNMP specification.

Microprocessor - The component of the computer's motherboard that interprets and executes instructions. The microprocessor, or CPU, is the "brain" of the computer.

Microwave - A wireless technology for transmitting data, usually between buildings due to the fact that it needs line of sight.

Mirroring - One disk acts as the primary storage disk, while the other provides a mirror image of the primary disk, providing redundancy in the event of a disk failure.

Modem - A device that enables a computer to transmit data over telephone lines. A modem converts the digital data that computers store into the analog waves that telephone lines transmit. Modem is an acronym for modulator-demodulator.

Monitoring - A program function that tracks the utilization of system resources.

NDMP - Network Data Management Protocol. Provides network-based backup of NAS devices.

NetWare - Novell's network operating system.

Network Attached Storage (NAS) - Hard disk storage that provides shared data to clients and servers on a LAN. NAS has a separate network address from the LAN computer that serves applications to users. This set up allows application programs and files to be served faster because they rely on different processor resources.

Network Operating System (NOS) - A computer operating system designed to support a network of workstations. It provides peripheral, application and database sharing across the network. Common NOSs are Windows NT/2000, Novell NetWare and Linux.

Network Interface Card (NIC) - A circuit board that is installed in a client or a server to enable it to connect to a network. Also called a network adapter.

NFS - Network file system.

NIS/YP - Network information services and yellow page. This is similar to DHCP, but it is for a Unix environment.

On-line expansion - The ability to dynamically expand a volume without downing the system or interrupting its operation.

Open-Source Software - Software that is freely available and can be modified by users.

Open systems - The characteristic of developing systems that meet industry-set standards, providing assured interoperability with systems from different manufacturers.

Operating System (OS) - The computer program that manages all application programs on a computer. It handles tasks such as determining which applications should run, the order they should run in, and how much internal memory they have allocated to them. The OS also communicates with users about operation status and errors.

Out of Band - The state of a server when it is not operational due to hardware failure or scheduled maintenance.

Parity - Extra information bits that are added to the data stream. If a disk failure occurs, the parity combined with the data on the remaining drives can be used to recreate the data on the lost drive.

Peer - A device on a peer-to-peer network. Each peer has equal responsibility in the network and operates with the same amount of power.

Peer-to-Peer Network - A network structure in which each workstation has equivalent capabilities. Peer-to-peer networks are an alternative to client/server networks. In general, they are simpler to set up and maintain but do not offer the same level of security or functionality. See also Local Area Network.

Peripheral - A computer or network device that is added to the core elements of a computer. Some can be included in the main computer itself, such as a CD-ROM drive; others, such as a printer, are attached to a computer's ports by cables or accessed through a shared network. A computer's bus allows peripherals to communicate with the CPU.

Plug and Play - An Intel standard for the design of PC expansion boards. It enables computers to recognize new peripheral devices without having to undergo additional configuration.

Ports - Sockets and/or plugs that physically connect computer devices or peripherals, such as hard drives and printers. A personal computer typically comes with ports built into it. Some ports that are commonly used today are Serial, Parallel, PS/2 and USB.

Proxy server - A program that acts as a liaison between a workstation and a Web server. A proxy server caches information to provide faster access to Web pages and increase network security.

Quota - Storage size control.

RAB - RAID Advisory Board.

Rack-mount - Industry standard communication and computer equipment rack cabinet.

Rack-Mount Server - A server with a form factor that is designed to fit inside an industry-standard 19-inch rack. The thickness of a rack-mount server is usually designated by unit size (U).

RAID - Redundant arrays of independent disks. A disk system with RAID capability can protect its data and provide on-line, immediate access to its data, despite a single (some RAID storage systems can withstand two concurrent disk failures) disk failure.

Random Access Memory (RAM) - The memory that temporarily stores program data actively running on a computer. Data stored in RAM is available only as long as a computer stays on. As soon as the computer is turned off, the data disappears.

Redundancy - The ability of a system to keep functioning normally in the event of a component failure, by having backup components that perform duplicate functions.

Replication - A method of replicating a collection of data on the server or volume.

Remote Access - The ability to connect to a computer or network from outside the network, usually via a telephone or cable line, or through a dedicated connection such as a T1 line. Users of remote access capabilities include telecommuters, traveling staff and other long-distance business affiliates. See also VPN.

Remote Access Server (RAS) - A server with modems that allows users to connect to the network using phone lines.

Remote Power Up - The ability to reboot the server from an offsite location.

Remote Support - The ability to run diagnostic programs and manage system troubleshooting from a remote location.

Router - A network device that determines where information packets traveling between networks should be directed by communicating with other routers and configuring the best route between any two hosts. Routers are located at the points where networks meet. See also hub, switch.

SAN - Storage area network. A dedicated network that connects storage devices and servers in a pool, providing consolidated storage and storage management.

Scalability - The ability for hardware and/or software to accommodate usage growth. Most companies consider scalability a desirable attribute because it allows them to invest in hardware and software that can grow with their businesses, rather than becoming obsolete as changes occur.

SCSI - A standard bus or interface between a computer and peripheral devices such as printers and disk drives. SCSI ports are supported by all major operating systems. SCSI stands for Small Computer System Interface and is pronounced "scuzzy." See also USB.

SCSI ID - Small computer systems interface address. Typically, there are 16 addresses on a single channel SCSI bus, such as SCSI Ultra160.

SCSI Ultra160 - A system level interface that uses high level commands and logical block addressing to transfer data at speeds up to 160MBps.

SCSI Ultra320 - A system level interface that uses high level commands and logical block addressing to transfer data at speeds up to 320MBps.

Server - A computer system that stores and serves application and data files to all users on a network.

Snapshot - A technology that provides instantaneous backups of data, providing a copy of the data as it appeared at a certain point in time.

SNIA - Storage Networking Industry Association.

SNMP - System network management protocol.

SSP - Storage service provider. A company that provides outsourced data storage space based on a "pay as you go" billing model.

Striping - Optimizes disk performance by enabling parallel disk input/output

Switch - A network component that controls connections between multiple nodes.

T1/T3 Connection - High-speed connections used by businesses or ISPs to access the Internet. A T1 line operates at 1.544 Mbps. A T3 line operates at 44.736 Mbps. See also cable modem service, DSL, ISDN, dedicated leased line, frame relay.

TCP/IP - Transmission Control Protocol/Internet Protocol. The communications protocol used by the Internet.

TCP/IP networks - By allowing SCSI commands to travel through IP networks, high-speed IP networking technology can carry data from storage units to servers anywhere throughout a corporate network. Also referred to as IP storage.

Terabyte (TB) - One trillion bytes, 1 million megabytes, or 1,000GB.

Throughput - The amount of I/O requests that can be completed within a given amount of time.

Token Ring - A type of LAN access technology based on a token ring (closed loop) topology. It transfers data across the network by passing a token from one resource to the next in a loop until it meets its final destination on the loop. See also Ethernet.

Topology - The physical arrangement of how devices are connected on a LAN or between two LANs. Common topologies include star, token ring and bus.

Twisted Pair - The standard copper wire used to connect homes and businesses to telephone service. A high grade of twisted wire is often used to wire LANs because it is less expensive than coaxial cable. The twisted pair wire typically used in LANs is Category 5 cable, or Cat 5.

Uninterruptible Power Supply (UPS) - A device that provides protection from power outages and surges. It contains a battery that keeps a computer operating for a short time when power is lost, allowing data to be saved and the computer to be properly shut down before damage occurs.

Universal Serial Bus (USB) - A plug-and-play bus or interface that allows peripheral devices such as printers and scanners to be added to a computer without an adapter card.

Unix - A computer operating system developed by AT&T's Bell Labs. Unix is an open system that can be modified by users such as individuals, universities and companies. See also Linux.

Virtualization - The technique of managing and presenting storage devices and resources functionally, regardless of their physical layout or location.

Virtual Private Network (VPN) - A technology that allows private, secure network connections between remote locations over the Internet. A VPN appears as a private network to the customer but uses the public network as its backbone. See also remote access.

VoIP - Voice over IP, a way of getting voice to work over IP networks, ideal for inter-office telephone calls.

WAN - Wide area network. A geographically dispersed network formed by linking computers or local area networks (LANs) together over long distances.

Web Admin - An administration tool that works under Internet browsers such as Internet Explorer or Netscape.

Web server - A server that delivers Internet pages to computers that request them.

WIN - Window name resolution services.

Windows Domain - A Windows Domain service that provides security for Windows networking.

Wireless Access Station - A device that connects wireless devices, including PCs, to a network.

Wireless LAN - A LAN that uses a wireless radio technology in place of cables to connect clients to the network.

Workgroup - A group of users involved in common projects who share computer files, usually over a LAN.

Write-back cache - An efficient cache technology that provides better performance than other caching methods.

Zoning - The process of dividing a storage area network into zones.