Measure Twice, Buy Once
There is a lot more that goes into purchasing a server rack than meets the eye. Not only do you need to know how wide your server is but how tall, how deep and how much space you are going to need around it as well.
Height is always the first dimension that people think of when they think of server racks. Where data centers today have a lot of space above their heads and server racks are going higher and higher, not all racks are created equal. The old ‘standard’ server rack was, on average, 42 Rack Units tall.
(Side note – if you are curious about what a Rack Unit is, you can find out Here!. )
Now server racks are going taller and taller. We even have a 58U (which tops the scale at 108 inches of pure server and computing power capabilities). The problem with going higher isn’t that IT professionals are short, and some of us are acrophobic, the problem goes into pulling out a server for upgrade or replacement and it’s weight, all from the top of a ladder. However if this isn’t an issue for you, then why not go up, the sky is the limit.
Also take into consideration, while a thousand U’s high may sound epic, unless your servers are weighing in at 3lbs or less per U, you may have to look at the weight capacity of your rack, as well as your floor tiles.
EIA measures a ‘standard’ server to be 19 inches. However, ever wonder why server racks are traditionally 24” wide? Floor tiles are a main reason. In metric countries, 600mm is the average server rack width for the same reason. In America, floor tiles for data centers (built extra tough to sustain the weight and heat of a data center floor) are 24” square. It’s necessary for the weight distribution and being better able to bolt down a server rack.
While height and width are the first things that pop into mind when looking at a server racks dimensions, depth is the most important. You could get a cabinet that’s only 24” deep to accommodate a small group of servers, you could go with one that’s 42 inches deep to accommodate a lot more, but the biggest depth for a cabinet or rack, without going custom, would be 48” deep. That extra space is really important. You can use the space, and depending on the rack you can make the space available in front of the shelf or server, behind, or a split between the two. This is a great place to put cabling, cable management; you can use it for PDU, power or any number of other uses. It could end up being the most useful space in your cabinet.