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Systems & Data Center · Foundational

Rack Unit

The standard unit of vertical height for rack-mounted equipment, equal to 1.75 inches (44.45 mm).

Definition

Server and network equipment is sized in rack units, such as 1U, 2U or 4U, and standard 19-inch racks are typically 42U to 48U tall. Planning rack space also considers power, weight, cooling and cable management.

Example

A 42U rack can hold twenty 2U servers plus two 1U top-of-rack switches.

Exam tip

1U equals 1.75 inches; rack width (19 inches) is a separate standard.

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