There have been a multitude of changes in the last decade of computers and information technology, particularly within the realm of sever racks. For example, the very term “server rack” has undergone significant change from its original definitions, when it sprung from the related terms of data cabinets, enclosure cabinets, and computer racks. These computer racks were originally designed to hold hardware for computers on nineteen inch rack rails. The first of these computer specific racks were widely distributed by Electronic Industries Alliance, or EIA.
Nineteen inch racks refer to standardized frames and enclosures created for the purpose of mounting several equipment modules. The term nineteen inches comes from the width of the front panel of each module; this width includes edges, also known as “ears”, that jut out from each side of the module, and enable personnel to fasten the module to the rack frame by use of screws.
Server racks originated as systems to mount railroad signaling relays. As a result, they are sometimes still called relay racks. However, the nineteen inch format width of the rack has remained through the years, although the equipment mounted within these racks has changed over the years to accommodate technology from a variety of fields.
Originally, the typical enclosure cabinet in the early server days maintained the nineteen inch module width and were twenty to twenty five inches in depth. This basic design remained the same for several years. However, as blade servers, or server computers stripped down and designed to fit in modules and optimized to use as little physical space and energy possible, became more popular in recent years, changes had to occur in the designs of enclosure cabinets. Before blade servers became increasingly popular, the typical server was either in a tower shape or came in a module between fifteen and twenty inches deep that would require 4U to 8U space for rack mounting. The “U” refers to “unit”, and refers to a region within a rack. The height of a space inside a rack is measured in Us; today, a computer that can be mounted in a rack is typically 1U or 2U higher, while an enclosure for a blade server may need 10U. For reference, a U is typically 1.75 inches high.
Initially, many well known blade servers on the market had been designed to make use of between 1U and 4U of space in a server rack. As a result, many more servers could be installed in a computer rack. However, when blade servers were inserted in the aforementioned U spaces, a problem arose as a result. Servers on the market began to be designed with significantly greater depth; some were forty two inches deep. They were also designed to run at hotter temperatures, with heat dispersal resulting from running air from the server’s front into the server and out behind it.
However, these new servers that were deeper in breadth and hotter in operating temperatures could not function well in the computer racks and enclosure cabinets that existed at the time, and to combat the premature failure rates, the computer rack industry developed a new style of rack to accommodate these new designs. A new computer rack had to be deeper to allow the servers to fit and had to have accommodations to allow air to flow from the front of the rack to the back, so servers would not overheat and shut down or fail altogether. This was the point where the term server rack began to be sued in place of the existing terminologies of computer rack, data cabinet, and enclosure cabinet.
Additionally, the existing standard of 10/32 tapped rack rails that had long been the default form of rack rail changed into a system involving punched square holes which held space for the insertion of cage nuts and screws. Today, many computer manufacturers make sliding rails that can be attached with special flanges to server racks; these flanges allow for fitting into the square holes without the need for rack screws, increasing functionality and the ability to swap modules on the fly.
Today, there are a variety of racks available, and changes continue to be made to optimize their storage capabilities.