When we think about today’s networks, all of the advanced technology enabling high-speed, low-latency transmission for the latest applications is pretty darn exciting. While racks and cabinets may not be the sexiest infrastructure component in your telecom spaces, they are an absolute necessity for housing and protecting the equipment that makes our digital world function—from the data center and main distribution frame (MDF) to the small office and intermediate distribution frame (IDF). But there is more to racks and cabinets than meets the eye and understanding the various types, sizes and features can go a long way in making the right choice for protecting your most important network assets.
Open Racks vs. Cabinets
Whether you choose an open rack or an enclosed cabinet has a lot to do with the type of equipment and the space. Open racks carry a lower price tag than enclosed cabinets and provide unobstructed airflow, easy access to equipment, and improved cable management. They come in 4-post and 2-post versions, with 4-post racks typically used for larger rack-mountable equipment such as servers, core switches and routers found in data centers, telecom central offices, and MDFs. They’re especially popular for housing carrier equipment in entrance facilities (i.e., demarcation points), colocation meet-me rooms, and other secured locations.
Smaller 2-post racks are ideal for mounting patch panels, switches and other standard-size IT components. They takes up less floor space and are therefore ideal for housing switches and patch panels in IDFs where backbone infrastructure transitions to horizontal infrastructure throughout a facility. They are also commonly used for housing cross-connects that contain multiple patch panels for distributing connections from one data center area to another. For example, in a hosted environment like a colocation data center, large cross-connects consisting of multiple open racks provide the connection point between carrier services in the meet-me room and tenant spaces.
Enclosed cabinets are better for housing servers and other equipment that requires protection and security in data centers, MDFs, and other telecom spaces. They prevent exposure to dust and debris, provide physical security, and offer better aesthetics. Enclosed cabinets also support air segregation such as in hot aisle/cold aisle configurations and containment, which is why they are often used to house large numbers of servers that generate heat and need to remain cool. Whether you need an open rack or an enclosed cabinet, there are multiple sizes and types to choose from and features to consider.
Know Your Size and Weight
When choosing a rack or cabinet, the first thing you need to know is how many rack spaces you need. In the networking world, a rack mount space (RMS), or rack unit (RU), is equal to 1.75 inches—it’s a standard that was established by AT&T over a century ago along with the 19-inch rack format and was later adopted as the EIA-310 standard by the Electronics Industries Association (EIA). But it’s not the height of a standard RMS that is a concern. The real concern is how many you need based on your active equipment (i.e., servers, switches, etc.) and their RU classification, as well as patch panels, PDUs, cable managers, or any other component that will occupy rack space. While the total RU of the equipment and components that will reside in the rack or cabinet will give you a good idea of the rack mount space you need, you should consider keeping some empty RUs for growth or additional components.
Most full size racks and cabinets range between 34RU and 45RU, with 42RU being the most common size for housing servers and equipment in larger data centers, central offices, and MDFs. Medium size 24RU and 28RU racks and cabinets are ideal for smaller telecom spaces such as IDFs throughout a facility or for MDFs in remote and small office environments. Small 18RU and 20RU racks and cabinets can also be used for smaller environments, as well as remote locations like a manufacturing floor, warehouse, or retail establishment. They are also often used for housing specialty equipment such as AV equipment. Where floor space is a concern, or in environments that only needs a maximum of about 12RU, it often makes more sense to go with a wall-mount rack or cabinet. We’ll take a closer look at these environments and wall-mount rack and cabinet options in an upcoming blog.
Free-standing racks and cabinets also have varying weight capacities so it’s important to choose one that can reliably hold the total weight of all planned equipment and components. Weight capacity has a lot to do with overall construction. Most cabinets and 4-post racks can hold more than a 2-post rack, but a sturdy 2-post steel rack bolted to the floor may provide just as much weight capacity as a cabinet. Additionally, a 45RU fully welded 14-gauge steel frame cabinet might accommodate up to 2500 lbs., while another 45RU cabinet may only support around 800 lbs. Higher weight capacity is typically required for large equipment such as core switches and routers but may also be required if you’re planning to fill the entire rack or cabinet with servers. It’s also important to check the weight capacity with or without casters as the use of casters can often decrease the load capacity.
Mounting Matters
Another major consideration when choosing rack or cabinet is depth. While 2-post racks are reserved for shallower equipment, 4-post racks and cabinets come in a variety of depths that range from about 20 inches to 40 inches to support larger equipment or mounting both at the front and the rear. It’s important to note that with cabinets, the advertised depth is typically usable depth—the actual dimension will be bit larger to accommodate for doors. Adjustable rails provide versatile mounting options, so it’s okay to have a rack or cabinet that is larger than some of your equipment.
While adjustable rails are ideal for supporting different equipment depths, you might also want to consider the type of rails. Over time, threaded holes can become stripped or damaged, potentially requiring rail replacement. In contrast, square holes are stronger and support cage nuts that provide threaded holes for a variety of equipment without worrying about stripping holes. Cage nuts can easily be snapped in and switched out with an inexpensive, easy-to-use cage nut tool. If a cage nut is stripped, you simply remove it and install a new one.
Cabinet Door Considerations
If you need an enclosed cabinet, you also need to choose a door style based on ventilation, accessibility, and security requirements. Solid doors are ideal for protecting equipment from unwanted viewing, while keeping out dust and debris. Glass doors also keep out dust and debris but offer equipment visibility. Vented or perforated doors promote better air circulation, which is helpful when housing servers that generate a lot of heat. If using solid or glass doors on the front of the cabinet, you may want to consider a vented door at the rear for exhaust, or actively removing heat with cabinet fans. You may also want to look for vented side panels for maximum air circulation. If using fans, be sure that your cabinet can accommodate them with the appropriate knockouts. Some cabinets come complete with preinstalled fans at the top of the cabinet to simplify on-site installation.
You also want your cabinet doors to ensure easy access to equipment and cabling—something that is not a concern with open racks. Depending on the cabinet orientation and space, you may need your cabinet door to swing to the right or left so it’s important to look for doors that can be mounted on either side. Double swing doors also offer access to both sides of the cabinets and removable or hinged side panels provide access for routing cables and servicing equipment. If security is a concern, look for locking doors and/or side panels.
The good news is that Cables Plus offers free-standing racks and cabinets of all sizes to support your equipment—from the data center and the telecom central office to the building’s MDF and IDFs. But we also know that with multiple rack mount space options, depths, construction, door styles, and accessories, choosing the right rack or cabinet is not always easy. Just contact us at