174 terms
Data center glossary
Plain-language definitions with real numbers. Free to cite with attribution.
24/7 carbon-free energy (24/7 CFE)
24/7 carbon-free energy is a sustainability standard requiring every megawatt-hour a facility consumes to be matched with carbon-free generation.
2N redundancy
2N redundancy means a data center installs two complete, independent systems, each capable of carrying the full load alone.
Adaptive Reuse
Adaptive reuse is the conversion of an existing building into a modern data center instead of constructing a new one.
Additionality
Additionality is the principle that a renewable energy purchase should cause new clean generation capacity to be built.
AI factory
An AI factory is a purpose-built data center engineered end-to-end to turn electricity and data into AI training and inference output.
Anchor Lease Term (Weighted Average Lease Term)
Weighted average lease term (WALT) is the average remaining duration of a data center operator's customer contracts, weighted by rent or contracted capacity.
Anchor Tenant
An anchor tenant is the first or largest customer that commits to a major share of a data center campus.
Arc Flash
An arc flash is an explosive release of energy caused by an electrical fault that travels through the air between conductors or from a conductor to ground.
Automatic Transfer Switch (ATS)
An automatic transfer switch (ATS) is a device that automatically switches a data center's electrical load to a backup source.
Availability zone (AZ)
An availability zone (AZ) is an isolated cluster of one or more physically separate data centers within a single cloud region.
Bare metal
Bare metal is a dedicated physical server rented to a single customer with no virtualization layer imposed by the provider.
Behind-the-meter power
Behind-the-meter (BTM) power is electricity generated at or adjacent to the consumption site, on the customer's side of the utility meter.
BESS (Battery Energy Storage System)
BESS (Battery Energy Storage System) is a grid-scale battery installation, almost always lithium-ion today, that stores electricity.
BMS (Building Management System)
A building management system (BMS) is the control layer that monitors and operates a data center's mechanical and electrical plant.
Bring Your Own Power (BYOP)
Bring Your Own Power (BYOP) is a development model in which a data center developer or tenant supplies its own generation.
Build-to-suit (BTS)
Build-to-suit (BTS) is a development model in which a data center developer constructs a facility to a specific tenant's requirements.
Busway (Busbar Trunking)
Busway, or busbar trunking, is a prefabricated metal enclosure carrying rigid copper or aluminum conductors that distributes power along a data hall.
C-rate
C-rate is a measure of how fast a battery charges or discharges relative to its rated energy capacity.
Cage (Colocation Cage)
A cage is a physically enclosed, lockable colocation space that gives one customer exclusive floor-level access control within a shared data hall.
Cap rate (capitalization rate)
Cap rate is the ratio of a property's annual net operating income to its market value or acquisition price, expressed as a percentage.
Capacity Factor
Capacity factor is the ratio of a power plant's actual generation over a period to what it would generate at full rated output the entire time.
Capacity market
A capacity market is a wholesale electricity mechanism that pays power generators and demand-response providers to guarantee available capacity.
Capacity Reservation
A capacity reservation is a contractual right for a tenant to hold future data center power and space for a fee before it is delivered.
Carrier hotel
A carrier hotel is a highly interconnected, carrier-neutral facility where telecom carriers, ISPs and enterprises physically meet to exchange traffic.
Carrier-neutral data center
A carrier-neutral data center is a facility whose owner does not favor or restrict access to any single telecommunications carrier.
CDU (Coolant Distribution Unit)
A CDU (Coolant Distribution Unit) is the hardware module that separates a data center's facility water loop from the technology cooling loop.
Cloud On-Ramp
A cloud on-ramp is a private data center connection that links a customer directly to a public cloud provider, bypassing the internet.
Colocation
Colocation is a service where a data center operator rents space, power, and cooling to customers for their own IT equipment.
Commissioning (Level 5 / IST)
Commissioning is the staged testing process that validates a data center's electrical and mechanical systems perform as designed.
Concurrently maintainable
Concurrently maintainable describes a data center design that allows planned maintenance on any power or cooling component without disrupting IT load.
Cooling Tower
A cooling tower is a heat-rejection device that removes heat from a data center's chilled-water or condenser-water loop.
Cost per megawatt (cost per MW)
Cost per megawatt is the total capital expenditure required to build one megawatt of critical IT capacity in a data center.
CRAC / CRAH units
CRAC (computer room air conditioner) and CRAH (computer room air handler) units are the workhorses of data center air cooling.
Critical IT Load
Critical IT load is the electrical power, measured in megawatts, that a data center can deliver to customers' IT equipment.
Cross-connect
A cross-connect is a physical cable link between two customers or between a customer and a carrier inside the same data center.
CUE (Carbon Usage Effectiveness)
CUE (Carbon Usage Effectiveness) is a sustainability metric that measures the CO2 emissions produced per unit of IT energy consumed in a data center, expressed in kgCO2e/kWh.
Curtailment
Curtailment is the deliberate reduction or halt of electricity generation or consumption below what would otherwise be available.
Dark fiber
Dark fiber is installed but unused (unlit) optical fiber that a customer leases and lights with its own transmission equipment.
Data Center Interconnect (DCI)
Data center interconnect (DCI) is a high-capacity network link between two or more data centers for sharing workloads and replicating data.
Data Center Moratorium
A data center moratorium is a temporary legal pause on new data center permits, grid connections or construction in a defined area.
Data hall
A data hall is the raised-floor or slab room inside a data center building where server racks, network gear and cooling units are installed.
DCIM (Data Center Infrastructure Management)
DCIM (data center infrastructure management) is software that monitors, measures, and manages a data center's physical infrastructure.
Debt yield
Debt yield is a lender's underwriting ratio that divides a property's net operating income (NOI) by the loan amount, expressed as a percentage.
Dedicated substation
A dedicated substation is an electrical substation built and reserved for a single data center campus.
Delta T (ΔT)
Delta T is the temperature difference between the coolant or air entering and leaving IT equipment or a cooling coil, expressed in degrees.
Demand charge
A demand charge is a utility fee billed on the single highest 15- or 30-minute peak of power draw (kW) during a billing period.
Demand response (load flexibility)
Demand response is a data center's ability to reduce or shift its electricity draw on request from a grid operator.
Design-Build-Operate (DBO)
Design-build-operate (DBO) is a delivery model in which one partner designs, constructs and then runs a data center for the asset owner.
Diesel Generator Set (Genset)
A diesel generator set, or genset, is an engine-driven generator that supplies backup power to a data center when the utility feed fails.
Digital twin (data center)
A digital twin is a continuously updated, real-time virtual replica of a data center's physical infrastructure.
Direct-to-chip cooling
Direct-to-chip (DTC) cooling circulates liquid coolant through cold plates mounted directly on the hottest components: CPUs, GPUs, and memory.
Dry Cooler
A dry cooler is a heat-rejection unit that cools a closed water or glycol loop by passing it through finned coils over which fans blow outdoor air.
Dual-Corded Power
Dual-corded power is a server power arrangement in which each device has two power supply units fed from two independent distribution paths.
Economizer (Airside/Waterside Economizer)
An economizer is a cooling-system mode that uses outside air or water conditions directly, bypassing energy-intensive mechanical chillers.
Edge data center
An edge data center is a smaller facility located close to end users or devices to minimize latency and backhaul costs.
Embodied carbon
Embodied carbon is the greenhouse gas emissions released in producing, transporting, and installing a building's materials and equipment.
Energization
Energization is the moment a data center is first connected to live utility power through its substation and switchgear.
Environmental Impact Assessment (EIA)
An Environmental Impact Assessment (EIA) is a formal study of a project's likely effects on water, air, noise, ecology and communities.
ERE (Energy Reuse Effectiveness)
Energy Reuse Effectiveness (ERE) is a data center sustainability metric that measures how much of a facility's total energy is reused elsewhere.
Fault Tolerant
Fault Tolerant describes an infrastructure design in which no single component or distribution path failure interrupts the critical load.
FFO / AFFO (Funds From Operations)
FFO (Funds From Operations) is the standard REIT profitability metric defined by Nareit.
Firm power
Firm power is electricity supply that a generator or utility contractually guarantees to deliver on demand, regardless of weather or fuel conditions.
Flexible Load
A flexible load is data center demand that can be reduced, delayed or shifted in time on request from the grid operator or utility.
Free cooling (economizer cooling)
Free cooling is a technique that removes heat from a data hall's cooling loop without running mechanical refrigeration compressors.
Front-of-the-meter (FTM)
Front-of-the-meter (FTM) describes generation or energy-storage assets that connect directly to the utility grid.
Gigawatt Campus
A gigawatt campus is a data center site planned or built to draw 1,000 MW (1 GW) or more of grid power, usually as several buildings on one contiguous parcel.
GPU cloud
A GPU cloud is a cloud service that rents GPU compute capacity, billed per GPU-hour or via reserved contracts.
Green Loan
A green loan is a debt facility whose proceeds are earmarked for projects with defined environmental benefits.
Greenfield development
Greenfield development is the construction of a data center on previously undeveloped land.
Grey space
Grey space is the area of a data center given over to mechanical and electrical support infrastructure.
Ground lease
A ground lease is a long-term agreement under which a data center developer leases raw land from its owner rather than buying it outright.
HBM (High Bandwidth Memory)
HBM (high bandwidth memory) is a type of DRAM in which memory dies are stacked vertically and connected to the processor over a very wide interface.
Heat Reuse Ratio
Heat reuse ratio is the share of the heat a data center produces that is supplied to another user instead of being rejected to the atmosphere.
Hot/cold aisle containment
Hot/cold aisle containment is a data center layout practice that physically separates cold supply air from hot exhaust air.
Hyperscale data center
A hyperscale data center is an extremely large facility built by or for major cloud and internet platforms.
Immersion cooling
Immersion cooling submerges entire servers in a non-conductive dielectric fluid that absorbs heat directly from all components.
In-Row Cooling
In-row cooling places cooling units between server cabinets in the same row rather than at the room perimeter.
InfiniBand
InfiniBand is a high-throughput, low-latency networking standard used to interconnect servers and storage inside data centers.
Interconnection
Interconnection is the direct exchange of traffic between networks, clouds, and enterprises inside or between data centers.
Interconnection queue
An interconnection queue is the ordered backlog of grid-connection applications that a utility or transmission operator must study and approve.
Internet exchange (IX / IXP)
An internet exchange (IX or IXP) is a shared switching fabric where multiple networks interconnect to exchange traffic directly.
IRR (Internal Rate of Return)
Internal rate of return (IRR) is the discount rate at which the net present value of a data center investment's projected cash flows equals zero.
IRU (Indefeasible Right of Use)
An IRU (Indefeasible Right of Use) is a long-term, non-cancellable right to use a specific amount of fiber capacity on a telecom route.
IT load
IT load is the electrical power actually consumed by computing equipment — servers, storage, and network gear — measured in kW or MW.
kW per rack (rack density)
kW per rack, or rack density, is the amount of electrical power a data center delivers to a single cabinet.
Large Load Tariff
A large load tariff is a utility rate class setting the terms on which very large customers, such as data centers, connect to the grid and buy power.
Latency
Latency is the time it takes data to travel between two points on a network, usually measured in milliseconds as round-trip time (RTT).
LCOE (Levelized Cost of Electricity)
LCOE (Levelized Cost of Electricity) is the average cost per unit of electricity that a generation asset must earn over its lifetime.
Lease-Up
Lease-up is the period after a data center phase is delivered during which its capacity is being sold until it reaches stabilized occupancy.
Levelized cost of storage (LCOS)
Levelized cost of storage (LCOS) is the average cost per unit of electricity a battery system discharges over its lifetime, expressed in $/MWh.
Liquid cooling
Liquid cooling is the use of fluids instead of air to remove heat from IT equipment.
Lit fiber
Lit fiber is a fiber-optic connection delivered with the provider's own transmission equipment already active on it, so the customer buys bandwidth.
Load Bank Testing
Load bank testing is the commissioning and maintenance practice of connecting artificial electrical loads to a data center's power systems.
Load Factor
Load factor is the ratio of average power drawn over a period to the peak power drawn in the same period, expressed as a percentage.
Loan-to-value (LTV)
Loan-to-value (LTV) is the ratio of a loan amount to the appraised or projected value of the asset securing it, expressed as a percentage.
Long-duration energy storage (LDES)
Long-duration energy storage (LDES) refers to storage technologies built to discharge continuously for roughly 8 to 100+ hours.
Long-Lead Equipment
Long-lead equipment is power and cooling gear, such as transformers, switchgear and generators, that takes many months to build and deliver.
M&O Stamp of Approval (Uptime Institute)
The M&O Stamp of Approval is Uptime Institute's certification of a data center's operational practices.
Meet-me room (MMR)
A meet-me room (MMR) is a secure, dedicated space inside a data center where networks physically interconnect via cross-connects.
Micro data center
A micro data center is a self-contained, factory-integrated unit of roughly 1-10 racks and 5-100 kW, often a single enclosure or container.
Microgrid
A microgrid is a localized power system, combining on-site generation with its own control system, that can run a data center.
Modular data center
A modular data center is a facility built from prefabricated, factory-assembled power, cooling and IT modules instead of entirely with on-site trades.
Monthly recurring charge (MRC / NRC)
Monthly recurring charge (MRC) is the ongoing monthly fee a colocation customer pays for space, power and cross-connects.
MTBF and MTTR (Mean Time Between Failures / Mean Time to Repair)
MTBF (Mean Time Between Failures) is the average operating time a piece of critical infrastructure runs before it fails.
MVA (Megavolt-Ampere)
MVA (megavolt-ampere) is the unit of apparent power, the product of voltage and current, used to size transformers, substations and grid connections.
N+1 redundancy
N+1 redundancy is a design approach in which a system has one more component than the minimum needed to carry the load.
Neocloud
A neocloud is a new generation of cloud provider focused almost exclusively on GPU compute for AI, in contrast to hyperscalers' broad service catalogs.
Net Absorption
Net absorption is a commercial real estate metric that measures the net change in leased or contracted data center capacity.
NOI (Net Operating Income)
NOI, or net operating income, is the revenue a data center property generates from rent, power and cross-connect fees minus its operating expenses.
NRC (Non-Recurring Charge)
A non-recurring charge (NRC) is a one-time fee billed at the start of a colocation or interconnection contract to cover setup work.
NVLink
NVLink is NVIDIA's proprietary high-speed interconnect that links GPUs to each other (and to NVIDIA CPUs) at far higher bandwidth than PCIe.
Open Compute Project (OCP)
The Open Compute Project (OCP) is an industry consortium that publishes open-source specifications for data center hardware.
PDU (Power Distribution Unit)
A PDU (power distribution unit) is equipment that distributes electrical power to IT hardware in a data center.
Peering
Peering is the direct, typically settlement-free interconnection of two networks to exchange traffic between their respective customers.
Planning Permission in Principle (PPiP)
Planning Permission in Principle (PPiP) is a Scottish planning consent route confirming whether a land use and scale of development are acceptable.
Point of Presence (PoP)
A Point of Presence (PoP) is a physical location where a network operator, cloud provider or CDN terminates its own infrastructure.
Power Capping
Power capping is the practice of limiting the electrical power a server, rack or whole cluster may draw to a fixed ceiling.
Power Density (W per square foot)
Power density is the amount of electrical power a data center supplies per unit of floor area.
Power factor
Power factor is the ratio of real power (kW) actually doing work to apparent power (kVA) drawn from the electrical supply.
Powered Land
Powered land is a site an operator has secured with a confirmed grid connection and allocated electrical capacity.
Powered shell
A powered shell is a data center building delivered with the core structure, secured utility power connection, and basic site infrastructure in place.
PPA (Power Purchase Agreement)
A PPA (power purchase agreement) is a long-term contract under which a buyer commits to purchase electricity from a specific generation project.
Prelease
A prelease is a lease commitment signed for data center capacity before the facility is completed — sometimes before construction begins.
PUE (Power Usage Effectiveness)
PUE (Power Usage Effectiveness) is a ratio that measures data center energy efficiency by dividing total facility power by the power delivered to IT equipment.
Rack density
Rack density is the amount of IT power, measured in kW, drawn by a single rack.
Rack unit (U)
A rack unit (U or RU) is the standard vertical measurement for equipment mounted in a data center rack, equal to 1.75 inches (44.45 mm).
Rack-Scale System
A rack-scale system is a pre-integrated AI computing unit designed, shipped and operated as one rack, not as separate servers.
Rail-optimized network
A rail-optimized network is a GPU cluster networking topology that connects the same-indexed NIC on every server to the same leaf switch.
Raised floor
A raised floor is a data center flooring system of removable tiles supported on pedestals 30-120 cm above the structural slab.
RDHx (Rear-Door Heat Exchanger)
A rear-door heat exchanger (RDHx) is a liquid-cooled panel mounted on the back of a server rack that removes heat from IT equipment exhaust air.
Ready for Service (RFS)
Ready for Service (RFS) is the milestone at which a data center building, hall or phase has passed commissioning and can be handed to the customer.
REC (Renewable Energy Certificate)
A Renewable Energy Certificate (REC) is a tradable instrument representing the environmental attributes of one megawatt-hour of renewable electricity.
REIT (Real Estate Investment Trust)
A REIT is a company that owns, operates, or finances income-producing real estate, including data centers.
Remote hands
Remote hands is an on-site technical support service offered by colocation providers.
Remote Power Panel (RPP)
A remote power panel (RPP) is a data hall cabinet that splits upstream feeds into branch circuits for racks.
Retail colocation
Retail colocation is the sale of data center capacity in small increments, bundled with power, cooling, connectivity, and support services.
Ride-Through Time
Ride-through time is the period a data center's UPS can carry the full IT load on batteries or flywheels after utility power fails.
Round-trip efficiency (RTE)
Round-trip efficiency (RTE) is the share of electricity a battery energy storage system returns compared with what it took in to charge.
Sale-leaseback
A sale-leaseback is a transaction in which a data center operator sells a facility it owns to an investor and keeps operating it under a lease.
SBTi (Science Based Targets initiative)
The Science Based Targets initiative (SBTi) is an independent body that validates corporate greenhouse-gas reduction targets.
Scope 1/2/3 Emissions
Scope 1, 2, and 3 emissions are the three categories in the GHG Protocol accounting framework used to classify a company's greenhouse gas footprint.
Scoping Report
A scoping report is the first document a developer files in a planning process.
Secured-Power Pipeline
A secured-power pipeline is the portion of a data center developer's planned capacity for which power supply has been contractually confirmed.
Shovel-ready site
A shovel-ready site is a parcel of land that has cleared the steps needed to begin construction immediately.
SLA (Service Level Agreement)
An SLA (service level agreement) is the contractual commitment a data center or service provider makes about measurable service quality.
Small Modular Reactor (SMR)
A Small Modular Reactor (SMR) is a nuclear fission reactor built well below the size of a conventional plant, typically under 300 MW per unit.
Solid oxide fuel cell (SOFC)
A solid oxide fuel cell (SOFC) is an electrochemical device that converts a fuel directly into electricity through a chemical reaction.
Sovereign AI
Sovereign AI is a nation's capability to independently develop, train, and operate artificial intelligence models.
Sovereign cloud
A sovereign cloud is a cloud infrastructure and service offering built to keep a customer's data within a specific national or regional jurisdiction.
Stabilized occupancy
Stabilized occupancy is the level of leased capacity at which a data center is considered fully ramped.
Stranded power
Stranded power is electrical capacity that exists but cannot be productively used or monetized — a growing theme on both sides of the data center market.
STS (Static Transfer Switch)
An STS is a solid-state switching device that transfers a load between two independent power sources when one fails or drifts out of tolerance.
Subsea cable (submarine cable)
A subsea cable (submarine cable) is a fiber-optic cable laid across an ocean or sea floor to carry internet and telecom traffic between countries and continents.
Switchgear
Switchgear is the assembly of circuit breakers, busbars, and protection and control equipment that distributes electrical power through a facility.
Take-or-Pay
Take-or-pay is a contract structure in which a customer commits to pay for a fixed quantity of capacity or power whether or not it actually uses it.
TDP (Thermal Design Power)
TDP (Thermal Design Power) is the maximum sustained heat, in watts, that a processor or accelerator is designed to dissipate, and the figure cooling systems are sized against.
Tenant Improvement Allowance
A tenant improvement allowance (TI allowance) is a landlord-funded contribution toward fit-out costs that a tenant incurs when taking space.
TIA-942
TIA-942 is an ANSI standard from the Telecommunications Industry Association that specifies requirements for data center infrastructure.
Tier Certification (Uptime Institute)
Tier Certification is Uptime Institute's formal, third-party verification that a data center's design and/or built facility meets a Tier level.
Time to Power
Time to power is the elapsed time between securing a data center site and receiving energized grid capacity at the contracted load.
Topping Out
Topping out is the construction milestone when the final structural element of a building, usually the highest beam or roof slab, is placed.
Total Cost of Ownership (TCO)
Total cost of ownership is the full lifetime cost of running IT capacity, not just the headline rent or hardware price.
Triple Net Lease (NNN)
A triple net lease (NNN) is a lease structure in which the tenant pays base rent plus property taxes, building insurance, and maintenance costs.
Ultra Ethernet
Ultra Ethernet is an open networking standard developed by the Ultra Ethernet Consortium to connect GPUs and accelerators inside AI clusters.
UPS (Uninterruptible Power Supply)
A UPS (uninterruptible power supply) is a system that provides instant backup power to IT equipment when utility power fails or fluctuates.
Uptime Institute Tier levels (I-IV)
Uptime Institute Tier levels are a four-level classification of data center infrastructure resilience, from Tier I (basic capacity) to Tier IV (fault tolerant).
Vacancy rate
Vacancy rate is the share of a data center market's built, powered capacity that is unleased and available for a new tenant to move into.
VPPA (Virtual Power Purchase Agreement)
A VPPA is a financial contract in which a data center operator agrees to pay a fixed price for electricity generated by a specific renewable project.
Waste Heat Reuse
Waste heat reuse is the practice of capturing the low-grade heat rejected by a data center's cooling systems and routing it to a productive use.
Wet-Bulb Temperature
Wet-bulb temperature is the lowest temperature air can reach by evaporating water into it.
White space
White space is the raised-floor or slab area within a data center that houses IT equipment: server racks, network gear and storage.
Wholesale colocation
Wholesale colocation is the leasing of large blocks of data center capacity to a single tenant under a long-term contract.
WUE (Water Usage Effectiveness)
WUE (Water Usage Effectiveness) measures data center water efficiency as liters of water consumed per kilowatt-hour of IT energy (L/kWh).
Yield on cost (YoC)
Yield on cost (YoC) is a real estate development metric: projected stabilized net operating income (NOI) as a percentage of total development cost.
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