Datacenter terms, in plain words.

The words that come up when you buy or sell capacity, explained without jargon. Every term links to itself, so you can share a definition.

Power and capacity

IT capacity: The power available to servers, storage and network equipment, in kilowatts (kW) or megawatts (MW). It excludes the power used for cooling and other building systems.
MW and kW: Units of power: 1 MW is 1,000 kW. Datacenter capacity is quoted as power rather than floor space, because power is usually the scarcer resource.
Rack density (kW per rack): The power one rack can draw. Ordinary servers use a few kilowatts per rack; AI and GPU racks often need 40 kW or more, which takes suitable power distribution and cooling.
PUE (power usage effectiveness): Total facility power divided by the power reaching IT equipment. A PUE of 1.0 would mean no overhead at all; the closer to 1.0, the more efficient the site.
Secured, applied and planned power: Secured power is contracted with the grid operator. Applied power has been requested and is waiting for a decision. Planned power has not been applied for yet.
Renewable power: Electricity from renewable sources such as hydro, wind or solar, supplied directly or matched with certificates of origin.
Heat reuse: Putting a datacenter's waste heat to use elsewhere, for example in district heating or industrial processes.

Air cooling: Cooling equipment with chilled air moved through the hall, usually arranged in hot and cold aisles.
Rear-door heat exchanger: A water-cooled door on the back of a rack that removes heat from the air as it leaves the servers.
Direct liquid cooling (DLC): Coolant piped to cold plates on the chips themselves. Common for high-density AI and GPU racks, where air alone is not enough.
Immersion cooling: Servers submerged in a non-conductive liquid that carries the heat away.
N, N+1, 2N and 2N+1: N is exactly the capacity needed, with nothing spare. N+1 adds one spare unit, so one component can fail. 2N duplicates everything, so either half can carry the full load. 2N+1 adds a spare unit on top of that.
Tier 1 to 4: A widely used classification of a datacenter's resilience, from basic capacity (Tier 1) to fault tolerance (Tier 4). Higher tiers add redundant power and cooling paths and allow maintenance without downtime.
ISO 27001, ISO 50001 and EN 50600: Common certifications: ISO 27001 covers information security management, ISO 50001 energy management, and EN 50600 is the European standard for datacenter facilities and infrastructure.

Colocation: Renting space, power and cooling in someone else's datacenter for your own equipment, from a few racks to whole halls.
Powered shell: A building with a grid connection and the basics in place, where the tenant designs and installs the data halls, cooling and racks.
Powered land: Land with a grid connection, secured or on the way, for building a new datacenter campus.
Datacenter offtake: A commitment to take capacity in a facility that is being built, often agreed before it is finished.
Ready date: When capacity can be handed over to the customer.
Site code: How AICapacity shows a site before both sides say yes, such as SE-1: the country and a number, never the name or exact location.

GPU compute: Access to graphics processors for AI training and inference, rented as servers or clusters rather than as space and power.
Bare metal: Whole physical servers dedicated to one customer, without a virtualisation layer in between.
Virtualised: GPUs offered through virtual machines running on shared physical hardware.
InfiniBand: A high-bandwidth, low-latency network often used to connect GPUs across servers for training.
RoCE: RDMA over Converged Ethernet: low-latency networking between GPUs over Ethernet, commonly at 100 or 400 Gb/s.

RFP (request for proposal): A description of what you need, sent to suppliers so they can answer with an offer. On AICapacity it takes a few minutes and stays anonymous until you choose to engage.
Fit score: A score out of 100 for how well a site meets a request, field by field, weighted by what the operator says matters most. An operator's plan never changes it.
Both say yes: AICapacity's rule for names: the operator says it is interested, the buyer chooses to engage, and only then do both sides see who the other is.
NDA (non-disclosure agreement): A contract that keeps shared information confidential. AICapacity offers a mutual NDA template both sides can start from.
LOI (letter of intent): A document setting out the main terms both sides intend to agree, before the full contract is negotiated.
Success fee: The share of contract value an operator pays on contracts signed through AICapacity, partly at signing and partly over the first months.