The rack server does not look like a computer, but like a switch, it has 1U (1U = 1.75 inches), 2U, 4U and other specifications. The rack server is installed in a standard 19-inch cabinet. Most of this structure is a functional server.

　　For information service companies (such as ISP/ICP/ISV/IDC), the server must first consider the physical parameters such as the size, power consumption, and heat generation of the server, because information service enterprises usually use a large dedicated computer room to uniformly deploy and manage a large number of The server room usually has strict security measures, a good cooling system, and a multi-backup power supply system. The cost of the machine room is quite expensive. How to deploy more servers in a limited space is directly related to the service cost of the enterprise. A rack server with a mechanical size conforming to the 19-inch industry standard is usually selected.

　　Rack servers are also available in a variety of sizes, such as 1U (4.45cm high), 2U, 4U, 6U, 8U, and more. Usually a 1U rack server is the most space-saving, but the performance and scalability is poor, suitable for some areas of relatively fixed business use. The products above 4U have high performance and good scalability. They generally support more than 4 high-performance processors and a large number of standard hot-swappable components. Management is also very convenient. Vendors usually provide corresponding management and monitoring tools, which are suitable for critical applications with large traffic volumes, but they are large in size and low in space utilization.