SERVER HARDWARE

Hardware requirements for servers vary, depending on the server application. Absolute CPU speed is not as critical to a server as it is to a desktop. Servers' duties to provide service to many users over a network lead to different requirements like fast network connections and high I/O throughput. Since servers are typically accessed over a network, servers emphasize function over form, without regard to aesthetics like appearance and noise level, because users may never lay eyes on the machine itself. Servers may accordingly run in headless mode without a monitor in order to free up processing cycles for other tasks. In general, a server becomes more specialized and therefore more efficient as unnecessary and unused services are eliminated. For this reason, many servers lack a graphical user interface, or GUI, because it consumes resources that could be allocated elsewhere. Similarly, servers often lack audio and USB interfaces.
By definition, servers provide services, but it is not always possible to predict when users will need those services. For this reason, servers are often online for weeks or months without interruption, making hardware durability extremely important. Although servers can be built from commodity computer parts, mission-critical servers use specialized hardware with low failure rates in order to maximize uptime. For example, servers may incorporate faster, higher-capacity hard drives, larger computer fans or water cooling to help remove heat, and uninterruptible power supplies that ensure the servers continue to function in the event of a power failure. These components offer higher performance and reliability at a correspondingly higher price. The dominant paradigm in servers is parallel computing, and thus high-performance servers are often placed in rack-mounted configurations to save space inside server rooms or "closets." These special rooms help mute the large amount of noise produced and also restrict physical access to the system administrators for security purposes.
Servers have a unique property in that, the more powerful and complex the system, the longer it takes for the hardware to turn on and begin loading the operating system. Servers often do extensive preboot memory testing and verification and start up of remote management services. The hard drive controllers then start up banks of drives sequentially, rather than all at once, so as not to overload the power supply, and afterwards they initiate RAID system prechecks for correct operation of redundancy. It is not uncommon for a machine to take several minutes to turn on and yet not require a restart for the next calendar year.