Racks are designed to hold equipment of those sizes. The holes in the mounting flanges of racks are arranged in groups of three, and that three-hole grouping is also called a rack unit. Jump to Category Jump to Brand Support Agent. Rack Unit Calculator toggle fractions What is a rack unit calculator used for? Rack unit calculator grid: Rack Units. Just like standard colocation server sizes, there are also standard rack sizes.
This infrastructure comes in a few dimensions. It should be noted: in terms of the colocation world, a half rack has a slightly different meaning than a simple calculation of half the server space.
Within the data center colocation world, a half rack is a unit which is 1U in height with only half the depth of a typical 4-post rack. The benefit of a half rack is that it allows for two 1U servers to be mounted side by side as opposed to one under the other.
One that is seven inches tall, for example, is given a rack unit size of 4U. Just how servers come in different sizes, racks come in different sizes, as well. Racks, which are almost always constructed entirely out of metal, are sturdy frames that hold individual servers. In other words, full racks hold about six feet of servers in terms of height. Half racks hold anywhere between 18 rack units and 22 rack units, or roughly three feet of servers stacked on top of one another.
Server racks also feature side-by-side columns to hold servers with. For instance, most optical disc players will not work upside-down because the driving motor mechanism does not grip the disc.
Racks are available with either four or two vertical rails. Four-post racks allow for mounting slides to support the equipment at the front and rear. These racks may be open in construction similar to the traditional open-style two-post racks , or may be enclosed by doors, side panels, or tops. Two-post racks provide just two vertical rails; a piece of equipment can be mounted either via its front panel holes, or close to its center of gravity to minimize load on its front panel.
Two-post racks are most often used for telecommunication installations. The posts are each 0. The posts have holes in them at regular intervals, with both posts matching, so that each hole is part of a horizontal pair with a center-to-center distance of The holes in the posts are arranged vertically in repeating sets of three, with center-to-center separations of 0.
The hole pattern thus repeats every 1. Racks are divided into regions, 1. Rack-mountable equipment is usually designed to occupy some integer number of U. For example, a storage array might be 4U high, and rack-mountable computers are most often 2U or 1U high. Occasionally, one may see fractional U devices such as a 1. This document is not the EIA document, but an aggregate of various source containing specification from EIA and other sources.
The specification also set tolerances on each of these dimensions. Vertical hole spacing is defined as a repeating pattern of holes within one Rack Unit of 1. See the diagram below. This dimension is not well maintained on some racks, causing problems with equipment installation. Many manufacturers use equipment mounting slots instead of holes to allow for variations in this dimension.
The opening in the rack is specified as a minimum of Square hole racks tend to be very close to the minimum opening. The term 19 inch comes from the width of the front panel of the boxes that are installed in the rack see the image below. The hole spacing for standard inch racks on the mounting flange is spaced in groups of three holes.
Manufactures of rackmount equipment make their product lines based upon how many rack units the equipment occupies in the server rack. The three hole group spacing is measured from center hole to center hole and does not vary regardless of whether the server rack has square or round mounting holes.
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