Server racks come in “standard” sizes to enable a consistent layout in the data center. The dimensions of IT equipment, on the other hand, can vary substantially. Although many manufacturers offer compact rackmount servers, more powerful systems may be too deep to fit into older racks. Additionally, modern equipment often requires more cabling, which must be accommodated within the cabinet.
The interior layout of the server rack is another variable. Some cabinets have more usable space than others, even within the same footprint. Server racks must be chosen carefully to avoid unexpected deployment problems.
Understanding Server Rack Sizes
Server racks are typically designated by height, measured in “rack units” or “Us.” A standard rack unit is 1.75 inches (44.45mm), so a 42U rack is 73.6 inches (1866.90mm) high. Data center equipment is also specified in rack units — a 2U server will take up 3.5 inches (88.90mm) of space.
Common Server Rack Sizes and Power Loads
The most popular modern server rack and cabinet dimensions are 24 inches (600mm) wide, 42 inches (1066.80mm) deep, and 73.6 inches (1866.90mm) tall. Those dimensions support most IT equipment and typically handle power loads of about 8kW per rack or less. However, the average power load per rack is constantly evolving as technology progresses, and there is some variability in rack size depending on the form factor of the environment's necessary IT equipment.
According to the Uptime Institute, the average power density per rack has grown from roughly 2.4kW in 2011 to 5.6kW in 2017 to 8.4kW in 2020. High-density rack configurations used to be about 16kW per rack, but with the proliferation of AI technology, that number has skyrocketed to 40kW or more for some organizations.
The most popular server rack size might not be the best choice for every use case. We will explore some of the most common server rack sizes (height, width, and depth) below.
Server Rack Height
Historically, 42U is the standard server rack height because it is tall enough to accommodate all necessary IT equipment but small enough to fit through standard door openings in trucks, building entrances, and elevators. They are unlikely to interfere with overhead sprinkler systems, and it’s easy to reach all of the rack positions without a stepladder. However, taller racks of up to 60U maximize the available vertical space in the same footprint if the data center can accommodate them.
Server Rack Width
“Standard” server rack width is 19 inches. Most data center equipment is designed according to that standard. 19 inches represents the usable space for mounting equipment (interior width). The exterior width is 24 inches (600mm), matching the traditional 24-inch by 24-inch tile in a data center-raised floor. Server racks are also available in 29.5-inch (750mm) and 31.5-inch (800mm) widths. Wider racks take up more floor space but provide more room for cable management and power distribution. They also support larger equipment such as blade servers, converged infrastructure and high-density network gear, and equipment with side-to-side cooling. In a previous blog post, we discuss variables to consider when deciding on a standard 19” rack width.
Server Rack Depth
As data center designs became denser, many manufacturers began offering server racks that were 36 inches (914.40mm) deep. This popularized the “seven-tile pitch” data center design, with aisles that are 24 inches wide and 14 feet long. Data centers still use server racks that are 36 inches deep, but they are also adopting deeper racks to accommodate deeper equipment.
The Server Rack Depth Conundrum
The problem is many of today’s more powerful servers are too deep to fit within 36 inches. Even if the server slides into the available server rack depth, there might not be enough space for PDUs and cable management. Low-profile power cords can free up some space, but these must be purchased from a third-party vendor.
It’s also important to remember that a designation of 36 inches represents the outside depth of the server rack. The interior space will obviously be less — much less, potentially, depending upon the cabinet design. What matters most is the distance from the front mounting rail to the PDU. If the server fits within this space, there will be plenty of room for PDUs and cables without impeding airflow or interfering with maintenance.
A server rack with an outside depth of 48 inches (1215mm) fits within two-floor tiles yet provides enough space for larger servers. Deeper racks of 59 inches (1500mm) are available, but they are more expensive and decrease the available rack space in the data center. We are also seeing racks with 42-inch or 43-inch depth be adopted.
There are many depth options out there, but the decision is simple. You need a rack that is deep enough to accommodate all equipment effectively and that utilizes available floor space efficiently.
Enconnex InfiniRack Cabinets
The Enconnex InfiniRack cabinet is nearly endlessly configurable to give you exactly what you need for your unique environment. Available in all the sizes you need, it was meticulously designed based on direct customer feedback and years of experience working with the biggest names in the data center industry. Some key features include maximum usable space, excellent load ratings (4,000 lb static and 3,000 lb rolling), dual integrated PDU channels for recessed PDU mounting, superior cable management options, heavy-duty swivel casters, and efficient airflow. Check out InfiniRack on our catalog to get more details.
Enconnex understands the needs of all types of data centers and engineered the InfiniRack to streamline installation and operations. Get in touch today to see how InfiniRack can support your IT initiatives.
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