Data Center Definitions

This glossary explains the meaning of key words and phrases that information technology (IT) and business professionals use when discussing data centers and related software products. You can find additional definitions by visiting WhatIs.com or using the search box below.

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  • I

    ISO (International Organization for Standardization)

    ISO (International Organization for Standardization) is a worldwide federation of national standards bodies.

  • ISO 50001 (International Organization for Standardization 50001)

    ISO 50001 is a standard for designing, implementing and maintaining an energy management system.

  • ISO 9000

    (For the business server line from Hewlett-Packard, see HP 9000.) ISO 9000 is a series of standards, developed and published by the International Organization for Standardization (ISO), that define, establish, and maintain an effective quality assurance system for manufacturing and service industries.

  • ITIL (Information Technology Infrastructure Library)

    The ITIL (Information Technology Infrastructure Library) is a framework designed to standardize the selection, planning, delivery, maintenance, and overall lifecycle of IT services within a business.

  • J

    JCL (job control language)

    JCL (job control language) is a language for describing jobs (units of work) to the MVS, OS/390, and VSE operating systems, which run on IBM's S/390 large server (mainframe) computers.

  • job

    In certain computer operating systems, a job is the unit of work that a computer operator gives to the operating system.

  • job scheduler

    A job scheduler is a program that enables an enterprise to schedule and, in some cases, monitor computer 'batch' jobs (units of work, such as the running of a payroll program).

  • K

    kernel

    The kernel is the essential center of a computer operating system (OS).

  • kernel panic

    A kernel panic is a computer error from which the operating system (OS) cannot quickly or easily recover. The term applies primarily to Unix-based systems and to Mac OS X... (Continued)

  • kernel-based Virtual Machine (KVM)

    Kernel-based Virtual Machine (KVM) is a free, open source virtualization architecture for Linux distributions.

  • Kyoto cooling (Kyoto wheel)

    KyotoCooling is an energy-efficient free cooling system for data centers. Kyoto cooling uses outside air to remove the heat created by computing equipment instead of using mechanical refrigeration.

  • L

    leaf-spine (leaf-spine architecture)

    Leaf-spine is a two-layer network topology composed of leaf switches and spine switches. Leaf-spine is a two-layer data center network topology that's useful for data centers that experience more east-west network traffic than north-south traffic.

  • LEED (Leadership in Energy and Environmental Design)

    LEED (Leadership in Energy and Environmental Design) is an ecology-oriented building certification program run under the auspices of the U.S. Green Building Council (USGBC)... (Continued)

  • lights-out management (LOM)

    Lights-out management (LOM) is the ability for a system administrator to monitor and manage servers by remote control.

  • Linux distros (Linux distribution)

    A Linux distribution -- often shortened to "Linux distro" -- is a version of the open source Linux operating system that is packaged with other components, such as an installation programs, management tools and additional software such as the KVM hypervisor.

  • Linux kernel panic

    Linux kernel panic occurs when the operating system discovers a potentially fatal error that affects the Linux kernel.

  • Linux operating system

    Linux is a Unix-like, open source and community-developed operating system for computers, servers, mainframes, mobile devices and embedded devices.

  • Linux stream

    A Linux stream is information traveling in a Linux shell from one process to another via a pipe, or from one file to another via a redirect.

  • Linux swappiness

    Linux swappiness is the rate at which a Linux platform's kernel moves pages into and out of active memory.

  • load bank

    A load bank is a device that generates a prescribed amount of electricity draw to test the reliability of electrical switching, generator output, uninterruptable power supply (UPS) systems and cooling in a data center.

  • load shedding

    Load shedding is a reduction of power demand by a utility provider during peak or stressed times. Participants voluntarily reduce demand for utility power and rely on secondary sources for uninterrupted operation, or lower or lose power supply in an involuntary load shedding event.

  • logical volume management (LVM)

    Logical volume management (LVM), a form of storage virtualization, offers system administrators a more flexible approach to managing disk storage space than traditional partitioning.

  • M

    mainframe (big iron)

    A mainframe (also known as 'big iron') is a high-performance computer used for large-scale computing purposes that require greater availability and security than a smaller-scale machine can offer... (Continued)

  • Management and Operations (M&O) Stamp of Approval

    The Management and Operations (M&O) Stamp of Approval from the Uptime Institute is a certification of the critical facilities and management operations procedures of a data center.

  • Mathematical symbols

    This table contains mathematical symbols and links to definitions of what they represent and how they are used.

  • mechanical refrigeration

    Mechanical refrigeration, often referred to simply as refrigeration, is a process by which heat is removed from a location using a man-made heat-exchange system.

  • motherboard tattoo

    A motherboard tattoo is a unique code that can be written in the basic input/output system (BIOS) of a computer to ensure that system restore or diagnostic compact discs (CDs) will work only on the machine or line of machines with which the CDs are sold.

  • moves, adds and changes (MAC)

    Moves, adds and changes (MAC) keep computing equipment in line with user needs and up-to-date, with disciplined process management.

  • multi-core processor

    A multi-core processor is an integrated circuit (IC) to which two or more processors have been attached for enhanced performance, reduced power consumption, and more efficient simultaneous processing of multiple tasks.

  • multiprocessing

    Multiprocessing is the coordinated processing of programs by more than one computer processor.

  • MVS (Multiple Virtual Storage)

    MVS (Multiple Virtual Storage) is IBM's best-known operating system for mainframe and large servers. Released in 1974, MVS successor systems include OS/390 and z/OS.

  • N

    National Electrical Code (NEC)

    National Electrical Code (NEC) is a set of regularly updated standards for the safe installation of electric wiring in the United States.

  • Net-SNMP (Net Simple Network Management Protocol)

    Net-SNMP is a set of tools and libraries for implementing the Simple Network Management Protocol (SNMP) on enterprise networks.

  • O

    OLTP (online transaction processing)

    OLTP (online transaction processing) is a class of software programs capable of supporting transaction-oriented applications on the Internet.

  • Open Blueprint

    Open Blueprint is IBM's strategic view of the network computing services and the relationship between these services.

  • Open Compute Project

    The Open Compute Project is an initiative started by Facebook to share efficient server and data center designs with the general IT industry.

  • open data center

    An open data center is an IT facility that employs a clearly defined and standardized set of hardware and software products designed to make the data center interoperable with other IT facilities.

  • Open Rack

    The Open Rack specification is an open standard for server racks designed to integrate with other parts of Facebook's Open Compute Project (OCP).

  • Open Vault

    Open Vault is an open-source storage specification created by Facebook and the Open Compute Project (OCP).

  • OpenPower Foundation

    The OpenPower Foundation is an organization in which IBM shares its Power microprocessor technology with licensed members.

  • out-of-order execution (OoOE)

    Out-of-order execution (OoOE) is an approach to processing that allows instructions for high-performance microprocessors to begin execution as soon as their operands are ready.

  • P

    parallel processing

    Parallel processing is a method in computing of running two or more processors (CPUs) to handle separate parts of an overall task.

  • Paris Agreement

    The Paris Agreement is an international treaty that seeks to reduce the emission of greenhouse gases. The agreement is sponsored by the United Nations Framework Convention on Climate Change (UNFCCC) and seeks to limit temperature increases in the 21st century to below 2 degrees Celsius.

  • Peripheral Component Interconnect Express (PCIe, PCI-E)

    PCIe is a high-speed serial interconnection standard for connecting peripheral devices to a computer's motherboard.

  • pizza box server

    The term "pizza box server" refers to the shape of a computer server enclosed in a rectangular and horizontally-arranged chassis and often installed in a rack with similar servers.

  • plenum

    In buildings, a plenum is a separate space provided for air circulation for heating, ventilation, and air-conditioning (sometimes referred to as HVAC) and typically provided in the space between the structural ceiling and a drop-down ceiling.

  • power cycling

    Power cycling is the process of turning hardware off and then turning it on again. In the data center, technicians use power cycling to test the durability and reliability of network components.

  • power distribution unit (PDU)

    A power distribution unit is a device for controlling electrical power in a data center. Floor and rack-mounted PDUs can provide data for power usage effectiveness (PUE) calculations.

  • power usage effectiveness (PUE)

    Power usage effectiveness (PUE) is a metric used to determine the energy efficiency of a data center. PUE is determined by dividing the amount of power entering a data center by the power used to run the computer infrastructure within it. (Continued...)

  • Puppy Linux

    Puppy Linux is a compact version of Linux, an operating system (OS) that provides computer users with a free or low-cost alternative to Unix. Puppy Linux is one of several similar OSs, all of which together make up a group called skinny Linux... (Continued)

  • R

    raceway

    A raceway is an enclosed conduit that forms a physical pathway for electrical wiring and protect wires and cables from heat, corrosion, water intrusion and other environmental threats.

  • RAIN (redundant/reliable array of inexpensive/independent nodes)

    RAIN (also called channel bonding, redundant array of independent nodes, reliable array of independent nodes, or random array of independent nodes) is a cluster of nodes connected in a network topology with multiple interfaces and redundant storage, providing fault tolerance and graceful degradation.

  • raised floor

    A raised floor is a data center construction model in which a slightly higher floor is constructed above the building's original concrete slab floor, leaving the open space created between the two for wiring or cooling infrastructure.

  • real-time operating system (RTOS)

    A real-time operating system (RTOS) is an operating system that guarantees a certain capability within a specified time constraint. For example, an operating system might be designed to ensure that a certain object was available for a robot on an assembly line. In what is usually called a "hard" real-time operating system, if the calculation could not be performed for making the object available at the designated time, the operating system would terminate with a failure. In a "soft" real-time operating system, the assembly line would continue to function but the production output might be lower as objects failed to appear at their designated time, causing the robot to be temporarily unproductive.

  • Red Hat

    Red Hat is a leading software company in the business of assembling open source components for the Linux operating system and related programs into a distribution package that can easily be ordered and implemented.

  • Red Hat Enterprise Linux (RHEL)

    Red Hat Enterprise Linux (RHEL) is a distribution of the Linux operating system developed for the business market... (Continued)

  • Red Hat Satellite

    Red Hat Satellite is an IT infrastructure management tool primarily used to monitor and manage Red Hat Enterprise Linux environments.

  • remote hands

    Remote hands is the general name for a service offered by colocation providers that enables customers to delegate IT management and maintenance tasks in a colocation facility to technicians hired by the provider.

  • Restriction of Hazardous Substances Directive (RoHS Directive)

    The Restriction of Hazardous Substances (RoHS) Directive is a set of criteria formulated by the European Union (EU) to regulate the use of toxic materials in electrical and electronic devices, systems, and toys... (Continued)

  • RPM Package Manager (Red-hat Package Manager)

    RPM Package Manager (RPM), originally called the Red-hat Package Manager, is a program for installing, uninstalling, and managing software packages in Linux.

  • rsync

    Rsync is a free software utility for Unix- and Linux-like systems that copies files and directories from one host to another. Rsync is available on most Linux distributions by default.

  • runlevel

    A runlevel is a Linux operating state that determines which programs can execute when the operating system restarts.

  • S

    scalability

    Scalability is the ability of a computer application or product (hardware or software) to continue to perform well when it (or its context) is changed in size or volume in order to meet a users need.

  • screen scraping

    Screen scraping is the act of copying information that shows on a digital display so it can be used for another purpose.

  • SELinux (Security-Enhanced Linux)

    SELinux, or Security-Enhanced Linux, is a part of the Linux security kernel that acts as a protective agent on servers.

  • server consolidation

    Server consolidation is an approach to the efficient usage of computer server resources in order to reduce the total number of servers or server locations that an organization requires.

  • server sprawl

    Server sprawl is a situation in which multiple, under-utilized servers take up more space and consume more resources than can be justified by their workload.

  • shell

    Shell is a UNIX term for the interactive user interface with an operating system.

  • shell script

    A shell script is a text file that contains a sequence of commands for a UNIX-based operating system.

  • single point of failure (SPOF)

    A single point of failure (SPOF) is a potential risk posed by a flaw in the design, implementation or configuration of a circuit or system in which one fault or malfunction causes an entire system to stop operating.

  • SMP (symmetric multiprocessing)

    SMP (symmetric multiprocessing) is the processing of programs by multiple processors that share a common operating system and memory.

  • software-defined everything (SDE)

    Software-defined everything (SDE) is an umbrella term that describes how virtualization and abstracting workloads from the underlying hardware can be used to make information technology (IT) infrastructures more flexible and agile.

  • statistical mean, median, mode and range

    The terms mean, median, mode, and range describe properties of statistical distributions.

  • supervisor call (SVC)

    In computers, especially IBM mainframes, a supervisor call (SVC) is a processor instruction that directs the processor to pass control of the computer to the operating system's supervisor program.

  • SuSE

    SuSE (pronounced soo'-sah) is a German Linux distribution provider and business unit of Novell, Inc.

  • SUSE Linux Enterprise Server (SLES)

    SUSE Linux Enterprise Server (SLES) is a Linux-based server operating system created and maintained by the German-based organization, SUSE.

  • SUSE Manager

    SUSE Manager is an open source infrastructure management tool for Linux systems.

  • sysplex and Parallel Sysplex

    A sysplex is IBM's systems complex (the word sysplex comes from the first part of the word system and the last part of the word complex), introduced in 1990 as a platform for the MVS/ESA operating system for IBM mainframe servers.

  • T

    TCO (total cost of ownership)

    Total cost of ownership is a calculation to assess direct and indirect expenses and benefits related to the purchase of a product or infrastructure component.

  • The Green Grid Performance Indicator (PI)

    The Green Grid Performance Indicator (PI) is a set of metrics designed to help information technology (IT) teams assess current and future data center cooling performance. PI was developed by The Green Grid in 2016.

  • the Open19 project

    The Open19 project is aimed at standardizing servers, storage and networking components into a common set of form factors for any Electronic Industries Association (EIA) 19-inch data center rack. The initiative was launched by LinkedIn Corp. in 2016.

  • total benefit of ownership (TBO)

    Total benefit of ownership is the sum of measurable and intangible returns that a company receives from investing in assets and/or personnel.

  • twin server (0.5 U server)

    A twin server has two compute nodes housed side-by-side in 1U of data center rack space. Because each server node fills half of 1U, a twin server may also be referred to as a 0.5U server.

  • twisted pair

    Twisted pair is the ordinary copper wire that connects home and many business computers to the telephone company. (Continued...)

  • U

    U (measurement)

    A U is a standard unit of measure for designating the height in computer enclosures and rack cabinets.

  • Ubuntu

    Ubuntu (pronounced oo-BOON-too) is an open source Debian-based Linux distribution. Sponsored by Canonical Ltd., Ubuntu is considered a good distribution for beginners. The operating system is intended primarily for personal computers (PCs) but can also be used on servers. The word "ubuntu" is from the African Zulu language and translates as "humanity to others." (Continued...)

  • uninterruptible power supply (UPS)

    An uninterruptible power supply (UPS) is a device that allows a computer to keep running for at least a short time when the primary power source is lost.

  • Unix

    Unix -- often spelled UNIX, especially as an official trademark -- is a multi-user operating system designed for flexibility and adaptability.

  • Uptime Institute, Inc.

    The Uptime Institute, Inc. is a consortium of companies devoted to maximizing efficiency and uptime in data centers and IT (information technology) organizations... (Continued)

  • Uptime Institute’s data center tier standards

    The Uptime Institute’s data center tier standards are a standardized methodology used to determine availability in a facility.

  • utility computing

    Utility computing is a service provisioning model in which a service provider makes computing resources and infrastructure management available to the customer as needed, and charges them for specific usage rather than a flat rate.

  • V

    VSAM (Virtual Storage Access Method )

    VSAM (Virtual Storage Access Method ) is a file management system for IBM's larger operating systems, including its primary mainframe operating system, MVS, now called OS/390. (...Continued)

  • W

    Waste Electrical and Electronic Equipment Regulation (WEEE)

    Waste Electrical and Electronic Equipment Regulation (WEEE) is a directive in the European Union that designates safe and responsible collection, recycling and recovery procedures for all types of electronic waste. 

  • water cooling

    In computers, water cooling is a method used to lower the temperatures of computer processors, and sometimes other components such as graphics cards, using water rather than air as the cooling medium. (Continued...)

  • wetware

    Wetware refers to programmers, developers, systems administrators, cloud and IT architects and other employees that directly affect how servers, applications, networks and the rest of an IT system functions.

  • white box server

    A white box server is a generic server made from commercially available retail computer parts. The phrase "white box" merely indicates that the equipment is generic or brand-agnostic -- the server can be any color.

  • wireless sensor network (WSN)

    A wireless sensor network is a group of specialized transducers with a communications infrastructure that uses radio to monitor and record physical or environmental conditions.

  • workload

    In computing, a workload, typically, is any program or application that runs on any computer.

  • WUE (water usage effectiveness)

    WUE (water usage effectiveness) is a metric developed by The Green Grid nonprofit consortium to help data centers measure how much water a facility uses for cooling and other building needs.

  • Y

    Yellowdog Updater, Modified (YUM)

    Yellowdog Update, Modified (YUM) is a program that manages installation, updates and removal for Red Hat package manager (RPM) systems. YUM allows the user to update groups of machines without having to update each RPM separately.

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