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Considerations for Determining Rack Size

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What is a rack unit?

A rack unit, also known as “U”, “RU”, or “RMU”, was created by the Electronic Industries Alliance (EIA); it is the standardized unit of measurement in IT rack enclosures. 1U rack unit refers to 1.75 inches or 44.45 mm of vertical space. The most common rack sizes are 42U & 45U, and for high density equipment you can find racks up to 47U & 52U.

How many rack units are needed for the most common rack mount equipment?

  • Servers are commonly designed in 1U to 4U form factors. Higher density blade servers & modular servers require more rack unit space to house servers, therefore 7U and 10U configurations are quite common in these applications. Other types of servers and blade systems can also be found in miscellaneous rack “U” heights.
  • Networking equipment, common network switches and routers are typically 1U to 2U in size, whereas modular network switches can be over 20U.
  • Cable management panels, are generally designed in 1U form factor.
  • 1U or 2U horizontal rackmount PDUs are also readily available for power distribution.

What does “0U” mean?

“0U equipment” refers to rack mount equipment that does not occupy any rack “U” space within the racks mounting rails. A vertical PDU is commonly known as “0U PDU“; they are usually mounted on the flanks of the rear inside the server rack.

How many “U” should I get for a server rack?

The amount of rack space needed is determined by your application. To assess how many rack unit you need, you can simply add up the rack “U”s that your equipment requires, while also making sure to reserve some extra “U”s for future expansion.

Air Blanking Panels - Rack Airflow Management

It is always better to overestimate the space you need. For any unused rack “U”s, the empty space can be filled with air blanking panels to manage the airflow of the server rack.

What is the ideal rack solution for my application?

Austin Hughes offers over 500 server & IT rack models. Depending on your application, you may want ->

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