IT Glossary



rack unit (RU)

A standard increment used to express the height of a piece of rack-mounted computer or networking equipment, abbreviated as “U” and equal to 1.75 inches. For example, a server with a height of 4U takes up seven inches of vertical rack space. The most common dimensions for an industry-standard rack are 42U (73.5 inches) high and 19 inches wide.

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