Although servers can be built from commodity computer components—particularly for low-load and/or non-critical applications—dedicated, high-load, mission-critical servers use specialized hardware that is optimized for the needs of servers.
A server rack seen from the back
For example, servers may incorporate “industrial-strength” mechanical components such as disk drives and computer fans that provide very high reliability and performance at a correspondingly high price. Aesthetic considerations are ignored, since most servers operate in unattended computer rooms and are only visited for maintenance or repair purposes. Although servers usually require large amounts of disk space, smaller disk drives may still be used in a trade-off of capacity vs. reliability.
CPU speeds are far less critical for many servers than they are for many desktops. Not only are typical server tasks likely to be delayed more by I/O requests than processor requirements, but the lack of any graphical user interface (GUI) in many servers frees up very large amounts of processing power for other tasks, making the overall processor power requirement lower. If a great deal of processing power is required in a server, there is a tendency to add more CPUs rather than increase the speed of a single CPU, again for reasons of reliability and redundancy.
The lack of a GUI in a server (or the rare need to use it) makes it unnecessary to install expensive video adapters. Similarly, elaborate audio interfaces, joystick connections, USB peripherals, and the like are usually unnecessary.