Black Box Explains...Choosing cabinets and racks
Why cabinets? Why racks?
A cabinet is an enclosure with a door (or doors); a rack is an open frame. There are several things you should consider when you’re deciding whether you need an enclosed cabinet or a rack.
First, what equipment will you be putting in it? The extra stability of a cabinet might be important if you’re installing large, heavy equipment like servers. But if you need frequent access to all sides of the equipment, an open rack might be more convenient. And if your equipment needs a lot of ventilation, you’ll have to be more careful about the air supply if you enclose it in a cabinet.
Second, in what environment will you be installing it? If the environment is open or dusty, for example, you might need the extra protection of an enclosed cabinet. On the other hand, a rack might be perfectly adequate in a well-maintained data center.
Don’t neglect aesthetics. Will customers or clients see your installation? A cabinet with a door looks much neater than an open rack. When you’re trying to create a professional image, everything counts.
Finally, there’s security. An enclosed cabinet can be locked with a simple lock and key.
On the other hand, there are advantages to open racks, too. It’s easier to get at all sides of the equipment. But you’ll have to take other steps to keep the equipment secure-keeping it in a locked room, for example.
Both cabinets and racks come in all sizes and in many different installation styles. Some are freestanding; some are designed to be mounted on a wall. Others sit on the floor but attach to the wall for more stability.
If you need to set up your installation in a hurry, you can order a preassembled cabinet. You’re ready to load your equipment as soon as the cabinet arrives.
Choosing the right server cabinet.
Consider this quick checklist of features when choosing a server cabinet:
High-volume airflow. The requirements for additional airflow increase as more servers are mounted in a cabinet. Additionally, manufacturers are making servers narrower to increase available space. But with more servers in the same amount of space, heat buildup is frequently a problem.
Extra depth to accommodate newer, deeper servers.
Rails with M6 square holes. Although 10-32 tapped and drilled holes are sometimes still required, newer hardware has M6 square holes. Know which type of mounting equipment you’ll need.
Front and/or rear accessibility.
NEMA 12 certification.
The National Electrical Manufacturers’ Association (NEMA) specifies guidelines for cabinet certifications. NEMA 12 cabinets are constructed for indoor use to provide protection against certain contaminants that might come in contact with the enclosed equipment. The NEMA 12 designation means a particular cabinet has met the guidelines, which include protection against falling dirt, circulating dust, lint, fibers, and dripping or splashing liquids. Protection against oil and coolant seepage is also a prerequisite for NEMA 12 certification.
Organizations with mission-critical equipment benefit from a NEMA 12 cabinet. Certain environments put equipment at a higher risk than others. For example, equipment in industrial plants is subject to varying degrees of extreme temperature. Even office buildings generate lots of dust and moisture, which is detrimental to equipment. NEMA 12 enclosures help to ensure that your operation suffers from as little downtime as possible.
Choosing the right rack.
Before you choose a rack, you have to determine what equipment you need to house. This list can include CPUs, monitors, keyboards, modems, servers, switches, hubs, routers, and UPSs. Consider the size and weight of all your equipment as well. The rack must be large and strong enough to hold everything you have now, and you’ll also want to leave extra room for growth.
Most racks are designed to hold equipment that’s 19" (48.3 cm) wide. But height and depth may vary from rack to rack. Common rack heights range from 39" (99.1 cm) to 87" (221 cm).
Another measurement you should know about is the rack unit. One rack unit, abbreviated as U, equals 1.75" (4.4 cm). A rack that is 20U, for example, has 20 rack spaces for equipment, or is 35" high (88.9 cm).
Understanding cabinet and rack measurements.
The main component of a cabinet or rack is a set of vertical rails with mounting holes to which you attach your equipment or shelves. When you consider the width or height of the rack, clarify whether they are inside or outside dimensions.
The first measurement you need to know is the width between the rails. The most common size is 19 inches with hole-to-hole centers measuring 18.3 inches. But there are also 23-inch and 24-inch cabinets and racks. Most rackmount equipment is made to fit 19-inch rails but can be adapted to fit wider rails.
After the width, the most important specification is the number of rack units, abbreviated “U.” It’s a measurement of vertical space available on the rails. Because the width is standard, the amount of vertical space is what determines how much equipment you can actually install. Remember that this measurement of usable vertical space is smaller than the external height of the cabinet or rack.
One rack unit (1U) is 1.75 inches of usable vertical space. So, for example, a rackmount device that’s 2U high will take up 3.5 inches of rack space. A rack that’s 20U high will have 35 inches of usable space.
Because both racks and the equipment that fit in them are usually measured in rack units, it’s easy to figure out how much equipment you can fit in a given cabinet or rack.
Do you need a fan?
Even if your cabinet or rack is in a climate-controlled room, the equipment in it can generate a lot of heat. You may want to consider adding a fan to help keep your equipment from overheating. It’s especially important to have adequate ventilation in an enclosed cabinet.
Getting power to your equipment.
Unless you want to live in a forest of extension cords, you’ll need one or more power strips. Some cabinets come with power strips built in.
If you need to order a power strip, consider which kind will be best for your installation. Rackmount power strips come in versions that mount either vertically or horizontally. Some have outlets that are spaced widely to accommodate transformer blocks-a useful feature if your equipment uses bulky power transformers.
Surge protection is another important issue. Some power strips have built-in surge protection; some don’t. With all the money you have invested in rackmount equipment, you’ll certainly want to make sure it’s protected.
Any mission-critical equipment should also be connected to an uninterruptible power supply (UPS). A UPS keeps your equipment from crashing during a brief blackout or brownout and gives you enough time to shut down everything properly in an extended power outage. You can choose a rackmount UPS for the most critical equipment, or you can plug the whole rack into a standalone UPS.
Managing the cables.
Your equipment may look very tidy when it’s neatly stacked in a cabinet. But you still have an opportunity to make a mess once you start connecting it all. Unless you’re very careful with your cables, you can create a rat’s nest you’ll never be able to sort out.
There are many cabinet and rack accessories that can simplify cable organization. We have Cable Management Guides, Rackmount Cable Raceways, Horizontal Covered Organizers, Vertical Cable Organizers, Horizontal Wire Ring Panels, and Cable Manager Hangers-all designed to help you manage your cables more easily.
Plotting your connections in advance helps you to decide how to organize the cables. Knowing where the connectors are on your equipment tells you where it’s most efficient to run cables horizontally and where it’s better to run them vertically.
The important thing is to have a plan. Most network problems are in the cabling, so if you let your cables get away from you now, you’re sure to pay for it down the road.
Asking for help.
When you’re setting up a cabinet or rack, you have a lot of different factors to consider. Black Box Tech Support is always happy to help you figure out what you need and how to put it together. For cabinets and racks solutions, call our Connectivity Group at 724-746-5500, press 1, 2, 2.