Data Center Glossary

Data Center Glossary

For the beginners to understand  the Data Center better and quick, here are some of the general terms used in the Data Center.
The terms here are categorized in relation to Power, Thermal, Network and Racks and few given in General.

Network and Rack related terms in Data Center


Data Center


High Performance computing; a data center with above average kW loading, typically greater than 10 kW/rack.


Keyboard, Video, Mouse. An interface technology that enables users to access multiple servers remotely from one or more KVM sites.

MAC Address

Media Access Control address. A unique identifier added to network interface cards by the manufacturer that is necessary for communicating on networks.


Network Interface Card.  A computer hardware component that allows a computer to connect to a network.  NICs may be used for both wired and wireless connections.


Device for holding IT equipment, also called a cabinet.

Raised Floor

Metal flooring on *stanchions that creates a* plenum for air flow and cabling.


The ability of a data center to maintain service in spite of problems such as power outages, server failures or network link of failures.


Storage Area Network. A storage environment that provides access to block- level data in disk arrays running on a dedicated network. SAN’s are distinguished from NAS, which provide file-level data, and use an interface standard that makes them appear as local storage to the operating system.


Network Design, planning Data Center operations and enhancement require both physical and logical topologies.


Rack mount unit. The standardized height of one unit is 1.75″


Wide Area Network. The WAN is the backbone network that serves geographically disparate users – consisting of a combination of dedicated lines, virtual networks over the Internet and wireless technologies.


Wireless Access Point. A hardware device or configured node on a local area network (LAN) that allows wireless capable devices and wired networks to connect through a wireless standard, including Wi-Fi or Bluetooth.

Thermal Related Terms in Data Center


Air Conditioning


British Thermal Units per hour.  12,000 BTUh = 1 ton of cooling or 3.5kW

Cold Aisle

An aisle where rack fronts face into the aisle.  Child airflow is directed into this aisle so that it can enter the fronts of the rack in a highly efficient manner.

Cold Spot

An area in which ambient air temperature is below acceptable levels.


Computer Room Air Conditioner, that uses a compressor to mechanically cool air.


Computer Room Air Handler, that uses chilled water to cool air.


Chilled Water. Often seen on piping for chilled water return or chilled water supply.

Dead Band

An HVAC energy saving technique whereby sensitivity temperature set points of equipment are set more broadly to improve efficiency.

Delta T

Delta Temperature, the difference between the inlet and outlet air temperatures of an air conditioning system.


Dehumidifying / Humidifying.


Dew Point Temperature, the temperature at which air reaches water vapor saturation.


Gallons Per Minute


Hot Aisle Containment, system that directs heated air from the outlet side of the racks to the air conditioning equipment return ducts in a highly efficient manner.

Hot Aisle

The aisle between two rows of racks where the heat from the back of the IT equipment discharges.


Heating, Ventilation, and Air Conditioning system. The set of components used to condition interior air including heating and cooling equipment as well as ducting and related air flow devices.


Heat Exchanger, a device used to transfer heat energy, typically used for removing heat from a chilled liquid system.

Inlet Air

The air entering the referenced equipment.  For air conditioning equipment this is the heated air returning to be cooled, also called return air.  For racks and servers, this is the cooled air entering the equipment.


In Row Cooling, cooling technology installed between server racks in a row that delivers cooled air to equipment more efficiently.


Kilowatts of Cooling.  Alternate unit of measure for the cooling capacity of a *CRAH


Latent Cooling Capacity, cooling capacity related to the wet bulb temperature and objects that produce condensation.

Liquid Cooling

A general term used to refer to cooling technology that uses a liquid circulation system to evacuate heat as opposed to a condenser, most commonly used in reference to specific types of in-row or close-coupled cooling techniques.


A receiving chamber for air used to direct air flow.


Chilled airflow returning to cooling units without passing through IT equipment.  Also referred to as short cycling.


Return Air Temperature, the heated air returning  to air conditioning equipment.


Relative Humidity. The amount of water vapor present in air expressed as a percentage of the amount needed for saturation at the same temperature.


Revolutions Per Minute, used for measuring fan speeds or *flywheel rotation.


Roof Top Unit. An air handler designed for outdoor use mounted on a roof top


Standard Cubic Feet per Minute. The volumetric flow rate of a gas corrected to standardized conditions of temperature, pressure, and relative humidity


Sensible Cooling Capacity, cooling capacity related to dry bulb temperature and objects that do not produce condensation.

Set Point

Typically used in reference to air conditioning equipment thermostat temperature and humidity settings


Supply Air Temperature, the cooled airflow emitted from the air conditioning equipment.


A type of resistor with resistance varying according to its temperature.


Variable Frequency Drive

Waterside Economizer

An economizer  that redirects water-flow to an external Heat Exchanger when the exterior ambient air temperature is at or below a temperature required to chill water to a given set point, simultaneously shutting down the mechanical chiller equipment.

Power related terms in Data Center


Alternating current, is an electric current which periodically reverses direction, in contrast to direct current which flows only in one direction


Automatic Transfer Switch is an electrical switch that switches a load between two sources

Critical Load

Computer equipment load delivered by *PDU output.


Direct current, an electric current flowing in one direction only.

Dirty Power

An abnormality in the power quality that is being delivered to a system. These abnormalities can include low power factor, voltage variations, frequency variations, surges, and sags.


A mixture of sulfuric acid and water utilized in lead-acid battery systems.


Electrostatic Discharge, more commonly called static discharge.


Electro-Magnetic Interference. A disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction.


Emergency Power Off.


A rotating mechanical device that is used to store rotational energy. Serves same purpose as a battery system.


A number of occurrences of a repeating event per unit of time.  Represented in Hertz (Hz).


A device that converts mechanical energy to electrical energy for use in an external circuit.


Infrared spectrum used by thermal imaging technologies.


Kilovolt, or 1,000 Volts.


Kilovolt Amperes = voltage x current (amperage). Also referred to as the unit of measure for apparent power of a system.


Kilowatt, or 1,000 Watts


Kilowatt hours. Product of the power in kilowatts and the time in hours.


Lower Explosive Limit.  The lowest concentration (percentage) of a gas or a vapor in air capable of producing a flash of fire in presence of an ignition source (arc, flame, heat.)


Lithium Ion Batteries.

Line Noise

Distortions superimposed on the power wave form that causes electromagnetic interference.


Power Distribution Unit. A device fitted with multiple outputs designed to distribute electric power, especially to racks of computers and networking equipment located within a data center.


Power Factor, the ratio of the real power absorbed by the load to the apparent power flowing in the circuit.


Phase, electrical phase 1-3 as typically referred to in three-phase AC power distribution systems.


Programmable Logic Controller.  Often used to control critical power systems such as switchgear.


Preventive Maintenance. Maintenance that is regularly performed on a piece of equipment to lessen the likelihood of it failing.

Reactive Power

Value of power measured in VA and represented by VAr.

Real Power

Value of power measured in Watts. Sometimes referred to as Active Power.


Radio Frequency interference.


Rack Power Distribution Unit.


Remote Power Panel. Device that provides circuit (or pole) capacity so that you can easily expand your server capacity without adding PDUs.


Static Transfer Switch. An electrical device that allows instantaneous transfer of power sources to the load. This superior switching time means that if one power source fails the STS switches to the back-up power source so quickly that the load never recognizes the transfer made.


Uninterruptible Power Supply. Device used to supply short term power to computing equipment for brief outages or until an alternate power source, such as a *generator, can begin supplying power.


Vented Lead Acid.  Technology of battery designed with free flowing electrolyte where water can be added, contained in a clear glass case, and used in high-capacity situations.


Valve Regulated Lead Acid. Technology of battery designed with an enclosed electrolyte system where water is not added; typically used in cabinet enclosed systems attached directly to a UPS. 


Watts.  Measure for power.

Some General terms in Data Center


As A Service


American Society of Heating, Refrigeration, & Air Conditioning Engineers.


Co-Location. A general real estate term referring to the renting of wholesale Data Center space to multiple tenants, with shared common areas, entrances, power, and cooling.


Computer Room


Data Center


Data Center infrastructure Efficiency, is a measure that is calculated by dividing the IT equipment power consumption by the power consumption of the entire data center.  The inverse of this measure is *PUE.


Data Center Infrastructure Management comprises software tools for discovering, monitoring and controlling assets forming a data-center; includes both power and computing resources.


Emergency Operating Procedure (Plan). Plan of actions to be conducted in a certain order or manner, in response to an emergency event, such as an unplanned power outage.


The service of running servers on behalf of another party, allowing those organizations to focus on managing their applications, instead of hardware and operating system administration.


ntermediate Distribution Frame, a room that contains UPS power, cooling and a cable rack that interconnects and manages the telecommunications/internet wiring between an MDF and workstation devices


Internet Protocol. A communications technology using the internet for communications.

IP Address

A unique string of numbers separated by periods that identifies each computer using the Internet Protocol to communicate over a network.


IT Infrastructure Library. A set of service-oriented best practices to guide the data center in supporting the broader organization’s needs.


Keyboard, Video, Mouse.  An interface technology that enables users to access multiple servers remotely from one or more KVM sites.


Main Distribution Frame, a room that contains UPS power, cooling and equipment interconnects and manages the incoming telecommunications/internet wiring and distributes it to any number of IDF’s.


Method of Procedure. A step-by-step sequence for performing an operation. It tells the maintenance and operations technicians how to execute the actions in order to perform an operation. Sometimes called SOW (statement of work) or SOP (statement of procedure).


Need plus One, a redundancy concept where capacity is configured to including planned capacity plus one additional device to enable continued operations with the failure of one system in the configuration. This presumes immediate detection and remediation of the failed unit.


Operational level agreement.


Operating Expense, the ongoing expenses related to the operation of the data center.


Power over Ethernet, allows us to power small network-ready devices without a separate power supply.


Power Utilization Effectiveness, a measure of data center energy efficiency calculated by dividing the total data center energy consumption by the energy consumption of the IT computing equipment. This measure is the inverse of *DCiE.


Root Cause Analysis. A systematic process for identifying “root causes” of problems or events and an approach for responding to them. RCA is based on the basic idea that effective management requires more than merely “putting out fires” for problems that develop, but finding a way to prevent them.


Root Cause Elimination


Return On Investment, a measure of the amount of time required to cover an investment.


Rack Unit.


Service Level Agreements. An agreement negotiated between the IT department and a user or a vendor that specifies how a service will be delivered in terms of response times, max allowable down time and other performance parameters.


Statement of Procedure.


Statement (Scope) of Work.


A sturdy upright fixture that provides support for some other object.


The open area underneath a raised computer floor.  Also called a sub-floor plenum.


Uptime institute rating of the level of redundancy of an electrical system.