The 1U, 2U, 3U, 4U, 5U, 6U and 7U are all different sized rackmount servers, and the U following the number is short for unit. The number indicates the size of the rackmount, 1U being the smallest rackmount and 7U being the biggest rackmount. The picture, courtesy of Dell Inc., shows some Dell PowerEdge servers and examples of different rackmount units.

Below is a listing of each of the different units and their dimensions. Although the width and height of a rackmount may be standard, the depth of a rackmount may change, as shown below. If your rackmount server is going to be placed in a constrained area, confirm the exact dimensions with the rackmount manufacturer.

Most collocations and ISPs accept 1U, 2U or 5U chassis. However, we recommend verifying with whomever is planning to host your server to verify what they support and at what cost.

Chassis, Network terms, Rack mount

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