Blade Server

A blade server is a stripped-down server computer with a modular design optimized to minimize the use of physical space and energy. Whereas a standard rack-mount server can function with (at least) a power cord and network cable, blade servers have many components removed to save space, minimize power consumption and other considerations, while still having all the functional components to be considered a computer. A blade enclosure, which can hold multiple blade servers, provides services such as power, cooling, networking, various interconnects and management. Together, blades and the blade enclosure form a blade system (also the name of a proprietary solution from Hewlett-Packard). Different blade providers have differing principles regarding what to include in the blade itself, and in the blade system altogether.

In a standard server-rack configuration, 1U (one rack unit, 19" wide and 1.75" tall) defines the minimum possible size of any equipment. The principal benefit and justification of blade computing relates to lifting this restriction so as to reduce size requirements. The most common computer rack form-factor is 42U high, which limits the number of discrete computer devices directly mountable in a rack to 42 components. Blades do not have this limitation. As of 2009, densities of up to 128 discrete servers per rack are achievable with blade systems.