Data Center Vocabulary

Corey Northcutt    By under Telecom Marketing.

There are millions of copywriters and digital marketers on the web, but so few genuinely speak "data center".

This is actually how came to exist in the first place. After I sold all stake in my managed hosting company in 2010, brands came out of the woodwork asking for help with content and messaging.

Since then, our team has trained dozens on how to speak this language like the best of them.  The vocabulary list below is always where we start.


Server: Describes anything that sends data outwards. It could refer to hardware, software, or both. Frequently Google-Translated into an issue that someone is having with their waiter.

Client: It's the opposite of a server. You're viewing this page using a web client (possibly Google Chrome). You read your email using an email client. You get the idea.

Tower: A server that stands up vertical.  Cheap providers show theirs off.  Expensive providers hide theirs during tours.  Slightly cheaper to buy but take up a lot more space.

Rack-Mount: The opposite of a tower. You bolt this to a rack or cabinet.

Rack: Four vertical bars. Where you bolt your rack-mount servers.

Cabinet: An enclosed rack. Potentially locking/private.

Bread Rack: Just set your tower servers on this you filthy heathen.

Cage: A private section of the data center where one client keeps multiple racks.

1u (or unit): A 1.75-inch section of a rack. Racks are commonly 42u (or units), but there are other possibilities too. Rack-mount servers come in these sizes too (usually 1u or 2u).


Data Center: This is where people put servers. They usually have a killer Internet connection, routers, and climate control. Also, reliable power and security. Most assume that this means one building owned by own person. In my experience, it usually means one room, cage, or one row of cabinets in a shared building.

Carrier Hotel: One building with lots of smaller "data centers" in it. Most importantly, multiple network service providers (NSPs) that various managed service providers can choose to connect through. Generally carrier neutral.

Carrier Neutral: A data center that does not offer IP transit services (internet). Instead, tenants arrange agreements with other tenants directly for connectivity.

HVAC: Pronounced H-Vac. Those giant dumpster-looking metal boxes along the walls of a data center that regulate temperature and moisture. You might also hear CRAC (Computer Room Air Conditioning).

VESDA System: Very Early Smoke Detection Apparatus. Somebody is telling you that they have a nice smoke detector.

Dry Pipe: Fire suppression without water.

Hot/Cold Aisle: Servers shoot hot air out their backsides. That's the hot aisle and the other is colder.

PDU: A Power Distribution Unit. Usually looks like a longer version of the surge protector in your house with around 22 outlets. The nice ones let you remotely toggle power to certain outlets.

UPS: An Uninterruptible Power Supply. These are car batteries that keep things running long enough to turn on a big, loud diesel generator if the power goes out.

ASTS: Automatic Safe Transfer Switches. Typically for switching from unstable power to a backup source.

Generator: Keeps generating power if there's an emergency. Typically using diesel fuel.

Power Density: How much stuff you can put in a room before it gets too hot or you run out of power.

Man Trap:  Two locking doors with a space between.  They open one at a time so that you can't just grab somebody's core router and run.

Raised Floor:  Like ceiling tiles, but on the floor.  Could help with cable management or cooling.  Hotly debated whether this is universally helpful/necessary.


Router: A smart/powerful networking appliance. Like a server, could refer to software or hardware (but usually it's hardware).

Switch: A less-smart networking appliance.

Edge Router: Usually the first and last piece of hardware that touches a data center's network.

Distribution Switch: Connects the router to access switches. More powerful than an access switch.

Access Switch: You typically put one of these inside every rack/cabinet. It's the "dumbest", cheapest switch in the data center.

Fiber: Refers to fiber-optic cables. Typically faster than the regular ethernet cables that you probably use in your house.

Firewall: Protects something behind it from a variety of attack types. Once again, could refer to hardware or software.

Meet-Me-Room: One room in a building full of "data centers" where every network connects. Those operating bigger networks usually like to rent a few rack units in one of these. They're usually held hostage by one of 2-3 telecoms that nobody likes.. not least of which because they rent this space at 2x to 2000x the price.

Upstream: Who sells you your bandwidth.

Peering: How data centers and other major networks connect with one another. Sometimes for free. Sometimes not.

IP Address: Every server, client, router, switch, firewall, and so on will have one of these numbers.  Sometimes more.

IPv4: The old type of IP address consisting of four octets (123.456.789.123). We're running out of these, so somebody created a new version.

IPv6: The new type of IP address consisting of a much longer hash. These are being implemented to replace IPv4, albeit, excruciatingly slowly.

CIDR: Stands for Classless Inter-Domain Routing.  Pronounced like apple cider. Sometimes referenced as "CIDR Notation".  Used by a network administrator to describe a range of IP addresses in a way that confuses everybody that isn't.  Where /24 means 256 IPv4 addresses, /23 means 512, and /1 means the entire Internet.

Class C: They mean 256 IP addresses (/24) or the range that it's in (A.B.C.everything).  But did you catch the "classless" above?  Prepare for a network administrator to tell you that this no longer exists (despite what a billion black hat SEO specialists told you).


Transit: Or "IP transit". Access to the Internet.

Transport: Or "long-haul transport". Generally connect two buildings but not to the Internet.

Cross-Connect: Think of it like "short-haul transport". Or, a 10-foot cable that you get to rent for some absurd monthly fee because you don't own the hallway between yours and the cage next door.

Dark Fiber: Fiber-optic cables that have been installed/buried but are not yet in use.

Colocation: You put your servers in somebody else's data center. Generally in racks, cabinets, or cages. Sometimes called "colo" or spelled with an additional "L" or with a hyphen... everybody seems to disagree on that bit so obviously, I'm the only one that's right.

Managed Services: Telecoms use this to describe anything that happens that's related to software.  Most facilities won't even touch it.  They reserve that end of the service spectrum for managed providers that pay them.  Who pretty much never use the phrase "managed services" themselves.  That's a vocab list for another time.

Remote Hands: An hourly fee that some providers charge to do just about anything involving your equipment or software.


Redundancy: Having more of a thing than you need. In any other world, that's bad. In a data center, it's good. This means that if your air conditioner, Internet, power, fire suppression, or anything else breaks, that you're (in theory) still fine.

Single Point of Failure: Any part of a system that isn't redundant.

N+1: Describes how redundant you are. This means one more than you need. You may also see N+2, N+3, etc. for two or three extras.

Diverse Paths: Or "diverse routes". Means that internet cables leaves the building in different directions. It's important because underground cables often get cut.


SSAE-16: A set of guidelines for data centers. Regular, 3rd-party auditing determines compliance. There are multiple "types". Most data centers are not SSAE-16 compliant and it's only important for delivering service to certain clients.

SAS70: The compliance audit that everybody underwent before SSAE-16. Means somebody needs to update their website and probably their compliance audits.

HIPAA: Similar to SSAE-16, a facility might undergo a compliance audit for HIPAA. The scope of HIPAA is more narrow and is only required for medical industry clients. Even fewer data centers are HIPAA-compliant.

Business Continuity: A well-designed plan for handling IT disaster. Required in many larger institutions, especially those publicly-traded.

Disaster Recovery: A subset of Business Continuity that's limited to off-site backup/recovery. Generally implies an expectation of SSAE-16 compliance.

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