Server Racks, Cabinets and Rack Shelves

Height in U and depth: what actually fits

Rack height is counted in U, and each U is 1.75 inches of vertical mounting space. A 12U rack suits a switch, a patch panel and a couple of servers, while 42U is a full floor cabinet. Equipment width is standardized at 19 inches, but depth varies: a short wall cabinet cannot take a deep server, so measure the deepest device and add room behind it for plugs and cable bends. Two-post racks hold light network gear, while four-post and enclosed racks carry deep servers.

Shelves, load rating and mounting holes

A rack shelf takes gear that has no rails, such as a router or a mini PC. Check the shelf's depth, whether it is vented, and the weight it supports; ratings are often split into static load, for a resting rack, and dynamic load, for a rack on casters being rolled. Mounting holes are square, round or threaded, and cage nuts fit square holes, so make sure the hardware matches your rack. Steel carries more weight than ABS, which is common in small wall boxes.

Questions about Server Racks, Cabinets and Rack Shelves

What does 1U mean in a server rack?

One rack unit is 1.75 inches (44.45 mm) of height. A 2U server takes two units, and a 12U rack offers twelve in total, minus anything reserved for power strips, cable management or blanking panels.

How deep should the rack be?

At least the depth of your deepest device plus a few inches for cables and connectors at the back. Server depth is in the product specifications, and rack depth is the usable space between the front and rear rails.

Will rack equipment from different makers fit the same rack?

Most 19-inch rack gear fits any standard rack, but rails and hole types differ. Check whether your rack has square, round or threaded holes, and that the equipment's rail kit supports your rack's depth.