Data centres rely on a wide range of facilities, power, cooling, networking and resilience terminology. This A–Z glossary explains common data centre terms in clear, practical language, from airflow and availability to UPS systems, white space and zero downtime.
A
Airflow Management
The control and direction of cooling air through a data centre to prevent hot spots and improve cooling efficiency.
Availability
The proportion of time that a data centre service, system or facility is operational and accessible when required.
B
Blade Server
A compact server module designed to fit into a shared chassis that provides common power, cooling and networking.
Busway
An overhead or underfloor electrical distribution system used to deliver power flexibly to racks and equipment.
C
Cold Aisle
An aisle between equipment racks where server air intakes face each other and receive cooled supply air.
Colocation
A data centre service in which customers rent space, power and connectivity for their own IT equipment in a shared facility.
D
DCIM
Data Centre Infrastructure Management software used to monitor, plan and manage power, cooling, space and physical infrastructure.
Diesel Generator
A standby power source used to support the facility during extended utility power failures.
E
Edge Data Centre
A smaller facility positioned close to users or devices to reduce latency and support distributed computing.
Electrical Redundancy
The use of duplicate or alternative power paths and components so equipment can remain operational if one path fails.
F
Failover
The automatic or planned transfer of service to backup equipment or systems when the primary resource becomes unavailable.
Free Cooling
A cooling approach that uses favourable outside conditions to reduce reliance on mechanical refrigeration.
G
Generator
Backup electrical equipment that supplies power when the normal utility source is unavailable.
Grounding
The connection of electrical systems and equipment to earth to improve safety and protect against electrical faults.
H
Hot Aisle
An aisle where the rear exhaust sides of equipment racks face each other and release heated air.
Hot Aisle Containment
A physical enclosure that separates hot exhaust air from cooler supply air to improve thermal efficiency.
I
In-row Cooling
Cooling units installed within or alongside equipment rows to provide cooling close to the IT load.
IT Load
The electrical power consumed by servers, storage, networking and other computing equipment.
J
Junction Box
An enclosure used to safely house electrical connections and cable joins within the facility infrastructure.
K
kW (Kilowatt)
A unit of power equal to 1,000 watts, commonly used to describe rack, IT and facility electrical loads.
kWh (Kilowatt-hour)
A unit of energy representing one kilowatt of power used for one hour.
L
Latency
The delay between sending and receiving data across a network, often measured in milliseconds.
Load Bank
Equipment used to apply a controlled electrical load when testing generators, UPS systems and power infrastructure.
M
Meet-me Room
A secure area where telecommunications carriers and customer networks interconnect within a colocation data centre.
Modular Data Centre
A data centre built from prefabricated modules that can be deployed or expanded in stages.
N
N+1 Redundancy
A resilience design where one additional component is available beyond the number required to support the normal load.
Network Operations Centre (NOC)
A team or facility responsible for monitoring network performance, availability and operational incidents.
O
Out-of-band Management
A separate management path that allows administrators to monitor and control equipment even when the normal production network is unavailable.
Overhead Cabling
The routing of power or network cabling above racks, often using trays, ladders or busway systems.
P
PDU (Power Distribution Unit)
Equipment that distributes electrical power to racks and IT devices, often with monitoring or remote management features.
PUE (Power Usage Effectiveness)
A commonly used efficiency metric calculated by dividing total facility energy by the energy used by IT equipment.
Q
Quality of Power
The stability and suitability of electrical power supplied to equipment, including voltage, frequency and waveform quality.
R
Rack Unit (U)
A standard unit of vertical rack space equal to 44.45 mm or 1.75 inches.
Redundancy
The provision of additional systems, components or paths so services can continue if primary infrastructure fails.
S
Scalability
The ability of a data centre or system to increase capacity as demand grows.
Static Transfer Switch (STS)
A device that rapidly transfers a critical electrical load between two power sources with minimal interruption.
T
Tier Classification
A framework commonly used to describe data centre infrastructure resilience and maintainability, ranging from basic capacity to fault-tolerant designs.
Transformer
Electrical equipment that changes voltage levels for safe and efficient power distribution.
U
UPS (Uninterruptible Power Supply)
A system that provides immediate temporary power to critical equipment when the primary supply fails or becomes unstable.
Uptime
The amount or percentage of time that infrastructure or services remain available and operational.
V
Virtualisation
Technology that allows multiple virtual servers or systems to run on shared physical hardware.
Voltage
The electrical potential difference that drives current through an electrical circuit.
W
White Space
The data hall area used for racks, IT equipment and associated cabling, as distinct from supporting plant and facility spaces.
Water Usage Effectiveness (WUE)
A metric used to assess the amount of water consumed in relation to the energy used by IT equipment.
X
X-Connect (Cross-connect)
A dedicated physical connection between two parties or network services within a data centre or colocation facility.
Y
Yield
A general capacity-planning term referring to the useful output or capacity obtained from available data centre resources.
Z
Zero Downtime
An operational objective in which planned changes or failures do not cause a visible interruption to critical services.
Zone
A defined physical or logical area used to organise infrastructure, security, cooling or operational responsibility within a facility.
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