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Data Center Server Rack Sizing Guide

Posted on April 27, 2022
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Server rack sizes come in more options than most businesses fathom. Choosing the correct data center rack size for mounting your equipment properly can be a daunting task, especially when you have only a limited understanding of how the size differences affect your business.

Fortunately, it is easier to make an informed decision based on just a few variables. Knowing these variables and following a few general rules can help you land the best data center rack sizes that meet the requirements.

Now, we’ll start small with the datacenter server rack sizing guide and its implications.

Explaining the Datacenter Rack Sizing Unit U

The datacenter rack unit ‘U’ is the standard unit used to measure the height of the server racks, or in other words, the ‘U-spaces’. A single rack unit U amounts to a height of 1.75 inches and the standard height for server racks goes up to 6-7 feet but these can vary based on individual needs. There are rack units with much larger and smaller sizes than the specified standard, although you’ll quickly find why the industry prefers this standard.

Server Rack Height

Height is a usual factor in classifying servers into various types. Width and depth are often not the crucial metrics.

The standard unit for sizing up a rack server also indicates the height dimension. Needless to say, this is one of the most important dimensions to take into account when purchasing a server rack, and the industry offers a standard.

Currently, 42U, 48U are the most popular standards for server racks. The 48U racks are also called “seven-foot racks” which makes the term sufficiently self-explanatory. 42U racks have a height of around six feet.

42U racks have replaced other sizes as the industry favorite. This is because the height is large enough to accommodate the equipment and scale it over time but small enough to access, maintain, and manage the equipment easily. 52U is also growing in popularity for data centers now. They are roughly eight-foot in height. Moreover, there are half-racks, also called 22U and 27U racks.

Once again, you must perform sufficient research before opting for any of these for your databases. Lately, there has been a growing trend of developing server racks of non-standard sizes. They are especially abundant for open-frame racks. These racks offer tremendous variety in sizes. The maximum size here can go up to 70 U (roughly equating to 3 meters).

data center server rack

Server Rack Width

Usually, a server rack width of 19 inches is prevalent in the IT industry. The number closely corresponds with the typical rack-mounted equipment sizes, as a majority of them are 19 inches long.

Having the same rack size as the equipment helps it to mount with ease. You no longer have to worry about measuring the individual components of your equipment since the rack can easily fit the entire equipment.

A server rack with an internal spacing of 19-inches usually has an exterior width of 24 inches. Once again, this data center rack size helps with easy access and equipment manageability. Most floor panels are 24 inches x 24 inches. Racks of a similar width can use up the space efficiently as it takes up only one panel. It also makes it very easy for data centers to add cables, mount PDUs, and monitor equipment using the available space on the edge.

Server Rack Depth

The depth dimension comes with fewer options than height. Server depth is typically measured in inches and can be anywhere between 0 and 50 inches. Popular server depth options are 24inches and 48 inches. If you’re working with open-frame racks, a 29-inch depth will also be a good fit. Open-frame racks such as these work well with popular companies such as Dell, IBM, and HP. This makes them far more abundant than one would think. On the other hand, a 24-inch server works perfectly well for accommodating AV and network equipment, patch panels, etc. Depth greater than 48 inches will house larger equipment and give additional space for cable and equipment management.

Equipment size is less of an issue when it comes to the depth of a server. Data centers have plenty of flexibility when pairing a rack with the server. Most rack servers can easily adjust smaller equipment using rails.

It is important to understand the different rack types when it comes to server rack depth. 4-post racks and 2-post racks have an inherent difference in their construction due to the fact that they have different depths.

2-post racks are built using two vertically upright beams, making them easier to use and more suitable for lighter equipment such as routers, switches and patch panels. 4-post racks are built using four upright beams.

A caster kit can be used to convert a two-post rack into a four-post rack. 2-post racks may have some depth restrictions but they can have similar height measurements as a standard datacenter server rack. A height of 24U is typical with two-post-half-racks, while full-sized racks come around 45U.

In contrast, four-post racks are much sturdier and can carry much more weight. They are supported by four posts that connect to all of their rails and shelves. On the flip side, these racks will increase your mounting depth requirements.

Choosing the Right Size

At the beginning of the article, we talked about knowing the right rules for purchasing datacenter server racks. The first rule of thumb is ‘planning’. You must look at the layout and setup. Estimate your servers' exact width, length, and height and related equipment to purchase servers that smartly fit the requirements.

As you may have noticed, there are plenty of rack options to choose from whether you are setting servers for your business, to put up in your home or to suit a startup. Regardless of how grand or modest your plans are, the right rack size is available. Just make sure that the rack’s type and size neatly conform to your overall setup and installation plans.

Four-post racks are a good fit for medium or large-sized equipment since they are mounted from both the front and the back making your accessories secure. Also, mount your accessories in a lockable and enclosed server rack for extra protection.

A second rule is to overestimate the space your rack may need for easier scalability. While looking for a data center rack, put special emphasis on the floor space. Data center rack dimensions should exactly fit the dimensions of your floor panel for cleaner airflow. For any inevitable space, you can also install blank panels to make sure the airflow is not obstructed.

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