To the uninitiated, server racks may seem like nothing more than fancy metal shelves designed to hold computers. Yet, anyone who has needed to set up a data center can attest to the fact that there is much more at stake when setting up a server room. Aside from needing to appropriate plan out the arrangement of the room, one must fully understand the different types of racks that are available. Acquiring the wrong size, type, or variety could end up costing your company more than it was willing to invest in equipment.
Focusing on size and shape, it is important to know that server racks are measured through a system known as rack units, usually written as "RU" or "U." A single rack unit is equivalent to 1.75 inches in height. Network switches typically range between 1U to 2U, and servers are generally sized from 1U to 4U. Blade servers, on the other hand, start off at around 5U and can be much larger.
Width and depth of your server racks are equally important. You will find that the most commonly accepted measurements are 19 inches for the width and between 600mm to 1,000mm for the depth. While there are server racks that allow you to adjust the rear brackets, most rack mount servers have an adjustable mounting kit included. This will allow for the slight variations that exist between server sizes, granting a single rack multiple potential uses.
If you’re looking for the a benchmark by which to measure your purchase, you will probably find the 19 inch wide four-post rack a common sight amongst standard data centers. The height is likely to be around 42U, but many companies stick to half-height racks which are only 24U tall. This is not to suggest that these sizes are more efficient or in any way better than other potential models, they are simply the units that are most popular amongst businesses. Your company should invest in the rack size that best fits its data center while holding equipment safely and securely.
If you find that you are working in a building with extremely limited space, there are alternative options that can help. Try investigating open frame racks or small wall-mounted cabinets to help make up for the lack of room at your work place. It is important to know, however, that open frame racks often times have very specific mounting requirements, such as being bolting to the floor.