physics

Open Rack

Open Rack is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Open Rack rather than just read about it. In short: Open Rack is an Open Compute Project standard for a rack and power delivery architecture as an efficient, scalable alternative to the EIA-310 19-inch rack. It is designed specifically for large-scale cloud deployments.

Key takeaways

Open Rack belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Open Rack to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Open Rack from memory before moving on to harder problems.

Reference excerpt

Open Rack is an Open Compute Project standard for a rack and power delivery architecture as an efficient, scalable alternative to the EIA-310 19-inch rack. It is designed specifically for large-scale cloud deployments. There are several key design features intended to make equipment more efficient to deploy, support, and operate:

The power to all of the compute, storage, or network devices is supplied by a pair of busbars located in the rear of the rack. The bus bars are supplied with 48 V DC by a shelf of power supplies, which provides efficient conversion from the local (usually three-phase) AC mains supply. The IT equipment that fits into Open Rack is 537 mm (nominally 21 inches) wide and 48 millimetres (1+7⁄8 in) tall. This is a 20% increase in frontal area that provides more airflow to the IT devices, helping data centers to reduce cooling costs. The vertical spacing is also taller, to accommodate better airflow and enclosures with improved physical designs that do not sag and interfere with adjacent equipment. All cables and interconnects are accessed from the front of the rack and the IT equipment is hot-pluggable and serviceable from the front of the rack. Service personnel no longer access the rear of the rack or need to work in the hot aisle.

Specification

OpenU Open Rack rack units, also called OpenU or just OU, measure 48 mm in height and describe how tall a rack or piece of equipment is, similar to U when referring to traditional 19-inch racks. For example, a "2OU server" measures 96 millimetres (3+3⁄4 in) in height. An Open Rack consists of three modular zones: power, equipment, and cable. To maintain compatibility with existing server infrastructure, OU cabinets are the same 24-inch (610 mm) external width as conventional server cabinets. However, an OpenU is slightly taller, to improve airflow and cable management.

Power zones

Equipment bay An equipment bay is 21 inches or 533 millimetres wide. An equipment bay rests on support shelves and blind-mates with the power supply through busbars.

Open Rack Wide In April 2026, as part of a larger Open Data Center Ecosystem for AI announcement, OCP announced Open Rack Wide (ORW), a specification for large format gear racks beyond the original Open Rack specification.

External links Reference specifications and designs Rack & Power section of Open Compute Project website

References

Worked examples

Example 1 — a first encounter with Open Rack

Start with the simplest possible case. Write down what Open Rack claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Open Rack before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Open Rack ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Open Rack

In research: Open Rack appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Open Rack in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Open Rack is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer enclosure, Mechanical standards, Server hardware, so understanding it makes those chapters shorter.
In everyday life: Look for Open Rack outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Open Rack in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Open Rack means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Open Rack out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Open Rack in simple terms?

Why does Open Rack matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Open Rack?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Open Rack.