TGG Glossary | The Green Grid

This is a glossary of older terms. While many of the definitions are unchanged, some of the definitions may be out of date and some of the terms may no longer be in use in the Data Center industry. This legacy glossary provides definitions for hundreds of information and communications technology (ICT) and data center terms and acronyms. Arranged alphabetically and searchable, the glossary explains common industry vocabulary.

1 A B C D E F G H I J K L M N O P Q R S T U V W Z

10-BASE-R

IEEE 802.3 physical coding sublayer for serial 10 GB/s operation (see IEEE 802.3, Clause 49)

1000BASE-T

IEEE 802.3 physical layer specification for a 1000 MB/s CSMA/CD LAN using four pairs of Category 5 balanced copper cabling (see IEEE 802.3, Clause 40)

10BASE-CX4

IEEE 802.3 physical layer specification for 10 GB/s using 10GBASE-X encoding over four lanes over shielded balanced copper cabling (see IEEE 802.3, Clause 54)

10BASE-X

IEEE 802.3 physical coding sublayer for 10 GB/s operation over XAUI and four lane PMDs (see IEEE 802.3, Clause 48)

A-C DCE

Air-Cooled Data Center Equipment. Source: TGG

A1 (ASHRAE)

ASHRAE allowable thermal envelope as defined in Thermal Guidelines for Data Processing Environments that air cooled equipment operates within based on non-failure conditions. It presumes the air has a dry bulb temperature between 15 and 32 Celsius. Source: ASHRAE

A2 (ASHRAE)

A3 (ASHRAE)

A4 (ASHRAE)

Absorbed Electrolyte

See electrolyte, absorbed

ACGIH

American Conference of Governmental Industrial Hygienists

ACH

Air changes per hour. Typically referring to outdoor air changes per hour

Acoustics

Generally, a measure of the noise level in an environment or from a sound source. For a point in an environment, the quantity is sound pressure level in decibels (dB). For a sound source, the quantity is sound power level in either decibels (dB) or bels (B). Either of these quantities may be stated in terms of individual frequency bands or as an overall A-weighted value. Sound output typically is quantified by sound pressure (dBA) or sound power (dB). Densely populated data and communications equipment centers may cause annoyance, affect performance, interfere with communications, or even run the risk of exceeding OSHA noise limits (and thus potentially cause hearing damage), and reference should be made to the appropriate OSHA regulations and guidelines (OSHA 1996). European occupational noise limits are more stringent than OSHA's and are mandated in EC Directive 2003/ 10/EC (European Council 2003)

Active solar heating system

A heating system that uses solar energy to heat a fluid -- either liquid or air -- and then transfer the solar heat directly to the interior space or to a storage system for later use. Source: United States Department of Energy

AFR

Aggregation Link

An instance of a MAC-physical layer-medium physical layer-MAC entity between a pair of aggregation systems (see IEEE 802.3, Clause 43)

Aggregation Port

An instance of a MAC-physical layer entity within an aggregation system (see IEEE 802.3, Clause 43)

Aggregation System

A uniquely identifiable entity comprising, among other things, an arbitrary grouping of one or more ports for the purpose of aggregation. An instance of an aggregated link always occurs between exactly two aggregation systems. A physical device may comprise a single aggregation system or more than one aggregation system (see IEEE 802.3, Clause 43)

Agile Device

A device that supports automatic switching between multiple physical layer technologies (see IEEE 802.3, Clause 28)

AHU

Air-handling unit, which is a device used to condition and circulate air as part of a heating, ventilating, and air-conditioning (HVAC) system

Air

A classification type of data center cooling. Source: NVIDIA

Air Conditioner (AC)

A self-contained unit designed to perform the functions of cooling, circulating, filtering, dehumidifying or otherwise processing of air. It may also be equipped to perform the additional functions of heating or humidifying. It may be the air cycle type used in aircraft or the vapor cycle type applicable to ground or aerospace equipment. Excludes ENVIRONMENTAL CONTROL UNIT, PERSONNEL, SELF-CONTAINED. [ FIIG=A505G0;INC=06486 || DLIS || ISO 22745-11 Source: eOTD ECCMA Open Technical Dictionary is an ISO 22745 compliant dictionary managed by ECCMA

Air Cooled (A-C)

Power that is transferred directly the room air and cooled via traditional data center cooling. Source: ASHRAE

Air Cooling

See cooling, air

Air Economizer

See economizer, air

Air Flow

The designed direction air flow within equipment, typically front or rear. Source: Supermicro

Air Inlet Temperature

The temperature measured at the inlet at which air is drawn into a piece of equipment for the purpose of conditioning its components

Air Outlet Temperature

The temperature measured at the outlet at which air is discharged from a piece of equipment

Air Short-cycling

Air conditioners are most efficient when the warmest possible air is returned to them. When cooler-than-expected air is returned to the air conditioner, it will perhaps mistakenly read that as the space temperature being satisfied. This air short-cycling is because the air is not picking the heat from the space before returning to the air conditioner (see also Air, Bypass)

Air Space

Where the air space below a raised floor or above a suspended ceiling is used to recirculate information technology equipment room/information technology equipment area environmental air, the wiring shall conform to Article 645 of NFPA 70, National Electrical Code

Air- and Liquid-cooled Electronics

See electronics, air- and liquid-cooled

Air- and Liquid-cooled Rack

See rack, air- and liquid-cooled

Air- and Liquid-cooled Server

See server, air- and liquid-cooled

Air-cooled Data Center (ASHRAE glossary)

See data center, air- and liquid-cooled

Air-cooled Electronics

See electronics, air-cooled

Air-cooled Rack

See rack, air-cooled

Air-cooled System

See system, air-cooled

Air, Bypass

Air diverted around a cooling coil in a controlled manner for the purpose of avoiding saturated discharge air. On an equipment room scale, bypass air can also refer to the supply air that short-cycles around the load and returns to the air handler without producing effective cooling at the load

Air, Cabinet

Air (typically for the purposes of cooling) that passes through a cabinet housing data communications equipment

Air, Conditioned

Air treated to control its temperature, relative humidity, purity, pressure, and movement

Air, Equipment

Airflow that passes through the IT or data communications equipment

Air, Return (RA)

Air extracted from a space and totally or partially returned to an air conditioner, furnace, or other heat source

Air, Supply

Air entering a space from an air-conditioning, heating, or ventilating apparatus

Aisle, Cold

See hot aisle/cold aisle

Aisle, Hot

See hot aisle/cold aisle

Alternating Current (AC)

An electric current that reverses its direction many times a second at regular intervals, typically used in power supplies. Source: Oxford Languages

Ampere (A)

The SI unit of electric current. It is defined by taking the fixed numerical value of the elementary charge e to be 1.602 176 634 x 10-19 when expressed in the unit C, which is equal to A s, where the second is defined in terms of ΔνCs. Source: BIPM

Annunciator

The portion of a fire alarm control panel or a remote device attached to the fire alarm control panel that displays the information associated with a notification. Notifications may include alarm or trouble conditions

Anomaly

A discrepancy between the actual and desired characteristics of an item. This definition is derived from ANSI T1.416-1999 and ANSI T1.105-1995, which take precedence

ANSI

American National Standards Institute

Application Programming Interface (API)

A set of functions and procedures allowing the creation of applications that access the features or data of an operating system, application, or other service. Source: Oxford Languages

Array

A collection of data items usually laid out linearly in memory for simple access with an integer index from the base of the array. Many scientific applications use arrays to contain the dataset that they are analyzing. The larger the dataset, the larger the array size needs to be to fit the data

Artificial Intelligence (AI)

Computer systems able to perform tasks normally requiring human intelligence, such as visual perception and speech recognition. Source: IPCC

ASHRAE

American Society of Heating, Refrigerating and Air-Conditioning Engineers, a US Non-Profit professional organization of 50,000 members from over 132 nations, ASHRAE is a diverse organization dedicated to advancing the arts and sciences of heating, ventilation, air conditioning and refrigeration to serve humanity and promote a sustainable world. The green grid has a long history of collaboration with TC 9.9 and that organization is currently working a select liquid cooling topics, specifically IT design enabling multi-refresh liquid cooling and a total cost of ownership (TCO) calculator for liquid cooling data centers. Source: ASHRAE

Associate Member

A membership class available to non-profit organizations at a significantly reduced cost. Allows for access to the benchmarks under development on the condition of significant involvement in the development process. Each group has their own rules and requirements regarding associate membership. Contact SPEC for details

ASTM

American Society of Testing and Materials. Source: United Nations GHS

ASTM International

Formerly the American Society for Testing and Materials (ASTM)

AUI

Attachment unit interface

Auto-negotiation

The algorithm that allows two devices at either end of a link segment to negotiate common data service functions (see IEEE 802.3, Clause 28)

Availability

A percentage value representing the degree to which a system or component is operational and accessible when required for use

Availability Date

The date upon which that part of the system becomes generally available, that is available to anyone willing to pay the appropriate price and take immediate delivery

Backplane

A printed circuit board with connectors where other cards are plugged. A backplane does not usually have many active components on it in contrast to a system board

Balanced Cable

A cable consisting of one or more metallic symmetrical cable elements (twisted pairs or quads) (from ISO/IEC 11801)

Bandwidth

Data traffic through a device usually measured in bits per second

Baseline

For SPEC's purposes, baseline refers to a configuration that is more general and hopefully simpler than one tuned for a specific benchmark. Usually a baseline configuration needs to be effective across a variety of workloads, and there may be further restrictions, such as requirements about the ease-of-use for any features utilized. Commonly baseline is the alternative to a peak configuration.

Basis-of-design

A document that captures the relevant physical aspects of the facility to achieve the performance requirements in support of the mission (as stated in the owner's program document)

Battery

A container consisting of one or more cells, in which chemical energy is converted into electricity and used as a source of power. Source: Oxford Languages

Battery, VLA

Vented lead-acid battery

Battery, VRLA

Valve regulated lead-acid battery

Baud (Bd)

A unit of signaling speed expressed as the number of times per second the signal can change the electrical state of the transmission line or other medium. Depending on the encoding strategies, a signal event may represent a single bit, more, or less than one bit. Contrast with bit rate, bits per second (from IEEE 610.7-1995 [B38])

Bay

* A frame containing electronic equipment * A space in a rack into which a piece of electronic equipment of a certain size can be physically mounted and connected to power and other input/output devices

BBC

Battery Backup Unit. Source: OCP

BCF

Bioconcentration Factor. Source: United Nations GHS

BEC

Boiling Enhancement Coating: surface microstructure enhanced coating to improve heat transfer properties. Source: OCP

Benchmark

A reference point. Originally, a mark on a workbench used to compare the lengths of pieces so as to determine whether one was longer or shorter than desired. For computers, a benchmark is a test, or set of tests, designed to compare the performance of one computer system against the performance of others. A benchmark is not necessarily a capacity planning tool. That is, benchmarks may not be useful in attempting to guess the correct size of a system required for a particular use. In order to be effective in capacity planning, it is necessary for the test to be easily configurable to match the targeted use. In order to be effective as a benchmark, it is necessary for the test to be rigidly specified so that all systems tested perform comparable work. These two goals are often at direct odds with one another with the result that benchmarks are usually useful for comparing systems against each other, but some other test is often required to establish what kind of system is appropriate for an individual's needs

Benchmark Sponsor

Every benchmark code of SPEChpc96 has a technical advisor who is knowledgeable about the code and the scientific/engineering problem, possibly with the help of experts outside the SPEC organization

BERT

Bit error ratio tester

Binary

To be specific, binary refers to a numeric representation that is comprised of (frequently very long) sequences of only two values, usually 0 and 1. Deep down at their very core, most computers really only understand 0 and 1 (or in other words, some little bit of information is either "off" or "on"). Thus, the term binary is frequently used to describe anything already translated to the form that is closest to what the system understands natively

BIOS

Basic input/output system. The BIOS gives the computer a built-in set of software instructions to run additional system software during computer boot-up

Bipolar Semiconductor Technology

This technology was popular for digital applications until the CMOS semiconductor technology was developed. CMOS drew considerably less power in standby mode, and so it replaced many of the bipolar applications around the early 1990s

Bit Error Ratio (BER)

The ratio of the number of bits received in error to the total number of bits received

Bit Rate (BR)

The total number of bits per second transferred to or from the media access control (MAC). For example, 100BASE-T has a bit rate of one hundred million bits per second (108 b/s)

Blade Server

A 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 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 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

Blanking Panels

Panels typically placed in unallocated portions of enclosed IT equipment racks to prevent internal recirculation of air from the rear to the front of the rack

Blower

An air-moving device (also see fan)

BMS

Building management system

Bridge

A layer 2 interconnection device that does not form part of a CSMA/CD collision domain, but conforms to the ISO/IEC 15802-3: 1998 [ANSI/IEEE 802.1D, 1998 Edition]. A bridge does not form part of a CSMA/CD collision domain, but rather appears as a media access control (MAC) to the collision domain (see also IEEE 100)

British thermal unit (BTU)

The amount of heat needed to raise one pound of water at maximum density through one degree Fahrenheit, equivalent to 1.055 × 103 joules. Source: Oxford Languages

Bit time

BTU

British thermal units. The amount of heat required to raise one pound of water one degree Fahrenheit, a common measure of the quantity of heat

Building

A physical building designed to accommodate new IT equipment and power cooling infrastructure. Source: ASHRAE

Building Automation System (BAS)

Centralized building control typically for the purpose of monitoring and controlling environment, lighting, power, security, fire/life safety, and elevators

Bureau International des Poids et Mesures

French organization managing the Metric system or Le Système international d’unités (SI) or the System of Units (SI). Source: BIPM

Burst pressure

Minimum internal fluid pressure for catastrophic failure of a fluid coupling. Common failure mode under burst pressure conditions may be elastomeric seal excursion. Typical pressure limits for fluid coupling may be 2x to 5x operating pressure. Source: ASHRAE

Bus, Electrical

See bus, power

Bus, Power (or Electrical Bus)

A physical electrical interface where many devices share the same electric connection, which allows signals to be transferred between devices, allowing information or power to be shared

Bypass Air

See air, bypass

Carbon, an EPA targeted greenhouse element. Source: United States Department of Energy

Competent Authority. Source: United Nations GHS

Cabinet

Frame for housing electronic equipment that is enclosed by doors and is standalone. This is generally found with high-end servers