What is 1U, 2U, 3U, 4U, 5U, 6U and 7U?(What is, Concept and Definition)

The 1U , 2U , 3U , 4U , 5U , 6U and 7U are rackmount servers of different sizes, and the U following the number is the abbreviation for the unit.The number indicates the size of the rackmount, with 1U being the smallest and 7U being the largest.The image, courtesy of Dell Inc., shows some of the Dell PowerEdge servers and examples of different rack-mount units.

Below is a list of each of the different units and their dimensions.Although the width and height of a rack mount may be standard, the depth of a rack mount may change, as you can see from continued.If your rackmount server is to be placed in a restricted area, please confirm the exact dimensions with the rackmount manufacturer.

1U	19 "x 1.75" x 17.7 "19" x 1.75 "x 19.7" 19 "x 1.75" x 21.5 "
2U	19 "x 3.5" x 17.7 "19" x 3.5 "x 20.9" 19 "x 3.5" x 24 "
3U	17.1 "x 5.1" x 25.5 "
4U	19 "x 7" x 17.8 "19" x 7 "x 26.4"
5U	19 "x 8.34" x 19.67 "19.1" x 8.75 "x 26.4"
6U	19 "x 10.5" x 19.5 "
7U	17 "x 12.2" x 19.8 "

Most placements and ISPs accept 1U, 2U, or 5U chassis, however we recommend checking with whoever is planning to host your server to verify what is supported and at what cost.