explain

"U" is a unit that represents the external dimensions of rack servers. It is an abbreviation for unit. The detailed dimensions are determined by the Electronic Industry Association (EIA), an industry group.

The reason for specifying the size of the server is to keep the server in an appropriate size so that it can be placed on an iron or aluminum rack. There are screw holes for fixing the server on the rack. Align it with the screw holes of the server and fix it with screws.

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

The basic unit of thickness is 4.445cm. 1U is 4.445cm, 2U is twice as large as 1U and 8.89cm. That is to say, the so-called "1U server" is a product whose shape meets EIA specifications and thickness is 4.445cm. Products designed to be placed in 19 inch cabinets are generally called rack servers.

Placing the server on the rack is not only conducive to daily maintenance and management, but also can avoid unexpected failures. First, the placement server does not occupy too much space. Rack servers are neatly arranged in the rack, which will not waste space. Secondly, the connecting wires can also be neatly folded into the rack. Power cables and network cables can all be laid in the cabinet, which can reduce the number of connection lines stacked on the ground, thus preventing accidents such as kicking off wires.