What do the 1U and 2U in the server mean?

Meaning of U

"Debut! A new generation server with a thickness of only 1U" ---. I have often seen such sentences in the advertisements of PC servers recently, but what does "U" mean here?

In fact, U is a unit that represents the external dimensions of the server, and is an abbreviation of unit. The detailed size is determined by the American Electronics Industry Association (EIA) as an industry group. The reason for specifying the size of the server is to keep the server in the proper size for placement on an iron or aluminum frame. The rack has a screw hole for fixing the server, and it is aligned with the screw hole of the server and fixed by screws.

The specified size is the width of the server (48.26cm = 19 inches) and the height (multiple of 4.445cm). Since the width is 19 inches, the rack that satisfies this requirement is sometimes referred to as a "19-inch rack."

The thickness is 4.445cm as the basic unit. 1U is 4.445cm, and 2U is 2 times that of 1U is 8.89cm. In other words, the so-called "1U PC server" is a product that meets the EIA specifications and has a thickness of 4.445 cm. Products designed to fit into a 19-inch rack are generally referred to as rack servers.

Placing the server in a rack is not only good for routine maintenance and management, but it can also avoid unexpected failures. First, placing the server does not take up too much space. The rack server is neatly discharged into the rack without wasting space. Secondly, the connecting wires and the like can also be neatly placed in the rack. Power cables and LAN cables can be routed in the cabinet to reduce the number of cables that are stacked on the ground, thus preventing accidents such as kicking off wires.

Previously, the rack was mainly referred to as a large cabinet in the center of the computer. However, there have been many products for office use recently, and some racks are only about 30cm. When you want to reorganize the space where the server is placed in the office, can you consider buying it?