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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  • H

    hot/cold aisle

    Hot aisle/cold aisle is a layout design for server racks and other computing equipment in a data center. The goal of a hot aisle/cold aisle configuration is to conserve energy and lower cooling costs by managing air flow.

  • HP 9000

    The HP 9000 is a line of UNIX-based business servers from Hewlett-Packard (HP) with server models that span enterprise applications from the "entry-level" (branch or department-level computers, Web hosting servers, and so forth) through the midrange with needs for handling advanced enterprise resource planning (ERP) and analytical customer resource management (CRM) up to its high-end servers for very computing-intensive applications.

  • HP-UX

    HP-UX is the UNIX-based operating system for the HP 9000 series of business servers from Hewlett-Packard.

  • HVAC (heating, ventilation, and air conditioning)

    HVAC stands for heating, ventilation, and air conditioning.

  • hydrofluorocarbon (HFC) clean agent

    Data centers and telecom rooms use hydrofluorocarbon (HFC) clean agent systems for fire protection to avoid damaging electrical and electronic equipment.

  • I

    IBM Integrated Facility for Linux (IFL)

    The Integrated Facility for Linux (IFL) is a specialty engine processor on IBM System z mainframe servers that is dedicated to Linux workloads. Operational efforts, software costs, energy use and hardware footprint are reduced when Linux is deployed on IFL rather than general-purpose processors.

  • IBM Roadrunner

    Roadrunner is the fastest supercomputer in the world, twice as fast as Blue Gene and six times as fast as any of the other current supercomputers. IBM developed Roadrunner for the Los Alamos National Laboratory in New Mexico. (Continued...)

  • IBM System z Application Assist Processor (zAAP)

    The IBM System z Application Assist Processor (zAAP) is a specialty engine that provides a performance environment for Web-based apps and service-oriented architecture-based technologies, e.g. XML and Java.

  • IBM System z Integrated Information Processor (zIIP)

    IBM's System z Integrated Information Processor (zIIP) is a specialty offload engine that helps improve computing performance for a subset of mainframe workloads.

  • IMS (Information Management System)

    IMS (Information Management System) is a database and transaction management system that was first introduced by IBM in 1968. Since then, IMS has gone through many changes in adapting to new programming tools and environments.

  • indemnification

    In service level agreements (SLAs) and other legal contracts such as end-user license agreements (EULAs), indemnification is the part of an agreement that provides for one party to bear the monetary costs, either directly or by reimbursement, for losses incurred by a second party.

  • information technology (IT)

    Information technology (IT) is the use of any computers, storage, networking and other physical devices, infrastructure and processes to create, process, store, secure and exchange all forms of electronic data.

  • infrastructure (IT infrastructure)

    Infrastructure is the foundation or framework that supports a system or organization.

  • intelligent power management (IPM)

    Intelligent Power Management (IPM) is a combination of hardware and software that optimizes the distribution and use of electrical power in computer systems and data centers. While the installation of IPM involves up-front cost and ongoing maintenance, the technology can save money in the long term as a result of reduced electric bills, reduced downtime and prolonged hardware life... (Continued)

  • ISAM (Indexed Sequential Access Method)

    ISAM (Indexed Sequential Access Method) is a file management system developed at IBM that allows records to be accessed either sequentially (in the order they were entered) or randomly (with an index).

  • 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.

  • ISPF (Interactive System Productivity Facility)

    ISPF (Interactive System Productivity Facility) is the user interface and supporting programs that come with IBM's OS/390 operating system and that allow a company to configure and manage its system, add new system or application programs and test them...

  • ITIL (Information Technology Infrastructure Library)

    The ITIL (Information Technology Infrastructure Library) is a framework designed to standardize the selection, planning, delivery and maintenance 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 Entry Subsystem (JES)

    Job Entry Subsystem (JES) is a subsystem of the OS/390 and MVS mainframe operating systems that manages 'jobs' (units of work) that the system does. Each job is described to the operating job control language (JCL).

  • 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).

  • job step

    In certain computer operating systems, a job step is part of a job, a unit of work that a computer operator (or a program called a job scheduler) gives to the operating system.

  • 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.

  • limited combustible cable (LCC)

    Limited combustible cable (LCC), also called CMP-50 cable, is fire-resistant cable with insulation made of a synthetic material called fluorinated ethylene propylene (FEP).

  • Linpack benchmark

    The Linpack benchmark is a method of measuring the floating point rate of execution of a computer by running a program that solves a system of linear equations.

  • 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.

  • liquid-tight strain-relief connector

    A liquid-tight strain-relief connector is a special electrical connector or jacket used in cabling for electronic and computer systems where water or contaminant intrusion is a concern... (Continued)

  • 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.

  • Logwatch

    Logwatch is a log analysis program that parses through system logs and generates periodic reports based on criteria specified by the user. These reports are generated immediately after Logwatch has run (normally every night), and can be transmitted by e-mail to a network administrator.

  • 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.

  • 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 server computers.

  • 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.

  • Network Cabling Tutorials

    (From the Computer Technical Tutorials Directory) Network Cabling Tutorials Network Tutorial: Cabling Covers Unshielded Twisted Pair (UTP), Shielded Twisted Pair (STP), Coaxial Cable, Fiber Optic Cable, Wireless LANs, and provides some cable installation guidelines Color Cabling Shows cabling color codes for several types of copper and fiber cable.

  • 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.

  • OS/390

    OS/390 is the IBM operating system most commonly installed on its S/390 line of mainframe server.

  • 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

    P/390

    The P/390 is basically an IBM mainframe system adapted to run on a personal computer.

  • 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 building construction, a plenum (pronounced PLEH-nuhm, from Latin meaning full) 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... (Continued)

  • 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 a service offered by colocation providers that allows customers to delegate management tasks to a technician hired by the provider.

  • Remote Job Entry (RJE)

    Remote Job Entry (RJE) is a facility that allows remote computer users to submit a job (the running of a specific program or group of programs) to a centrally-located IBM mainframe computer.

  • Resource Access Control Facility (RACF)

    RACF (Resource Access Control Facility) is the IBM security management product for its mainframe (large server) operating system, OS/390 (MVS) as well as for its VM operating system.

  • 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)

  • Rexx

    Rexx is an interpreted script language developed by IBM originally for use by personal users of large operating systems.

  • RPM Package Manager (Red-hat Package Manager)

    RPM Package Manager (also known simply as RPM), originally called the Red-hat Package Manager, is a program for installing, uninstalling, and managing software packages in Linux. RPM was developed on the basis of the Linux Standard Base (LSB). In latter-day usage, the "RPM" portion of this term arises from the fact that .rpm is the default extension for files used by the program.

  • 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

    S/390

    S/390 is IBM's large server (or mainframe) line of computer systems, which are marketed to the world's Fortune 1000 and many mid-size companies as a "tried-and-true" system with a history that stretches back to the System/360 of the early 1960s.

  • scalability

    It is the ability of a computer application or product (hardware or software) to continue to function well as it (or its context) is changed in size or volume in order to meet a user 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 blade

    A server blade is a thin, modular electronic circuit board containing one, two, or more microprocessors and memory, that is intended for a single, dedicated application (such as serving Web pages) and that can be easily inserted into a blade server, which is a space-saving rack with many similar servers. One product offering, for example, makes it possible to install up to 280 blade server modules vertically in multiple racks or rows of a single floor-standing cabinet. Blade servers, which share a common high-speed bus, are designed to create less heat and thus save energy costs as well as space.

  • 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.

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