A rack is any freestanding frame that doesn’t have doors or sides. There are several things you should consider when choosing a rack. If you need frequent access to all sides of the equipment and cabling, an open rack is more convenient than a cabinet. If your equipment needs ventilation, a rack offers more air circulation than cabinets. With the open design, racks are a good choice in areas where security isn’t a concern, or inside data centers and closets with locked doors. And racks typically cost less than cabinets.
The best place to start when picking a rack is to ask yourself: What are you going to put in it? This will help you determine if you need a wallmount or a floor-mount model and whether you need a 2-post or a larger 4-post rack.
You have a number of options depending on the type of equipment you need to house. If you’re installing patch panels, a two-post rack with some cable management is the right choice. But if you have a mix of networking equipment, servers, and patch panels, then a 4-post rack makes more sense because it provides more stable, 4-point mounting for deep equipment. For flexible mounting of both standard and extra-deep equipment, you can even get four-post racks with rails that are adjustable front to back.
The main component of a rack if a set of vertical rails with mounting holes to which you attach your equipment or shelves. Most racks come in rails spaced at the EIA standard 19" with hole-to-hole centers measuring 18.3". To rackmount smaller equipment, add rackmount adapter brackets. For mounting older legacy equipment, there are 23" wide racks. Two-post racks typically have threaded 12-24 or 10-32 holes for quick installation of patch panels, and 4-post racks usually have M6 square mounting holes for mounting servers.
Height, or rack units, is one of the most important specifications in choosing a rack. One rack unit (1U) is 1.75" of usable space. So, forb example, a rackmount device that’s 2U high takes up 3.5" of rack space. Most freestanding racks come in a standard 45U height, which is 6.5 feet high, so they fit rooms with standard ceilings. But there are other height options — from smaller 10U-high wall mount models all the way up 58U- high units. These tall racks, towering up to 9 feet, allow for an extremely dense installation of equipment while saving floor space.
Wallmount-style racks save floor space, too. They’re very convenient for installing in cramped wiring closets or narrow hallways. Some even swing out for easy equipment installation and cable connections. Other low-profile racks enable you to flush mount equipment vertically against a wall to further reduce the amount of space they take up. Wallmount racks are typically designed to be installed on 16-inch-on-center studs or on backing boards attached to the wall.
Now that you’ve chosen a rack, you’ll need to get power to equipment. Rackmount power strips come in versions that mount either vertically or horizontally. Some have outlets that are spaced widely to accommodate transformer blocks.
Surge protection and power management is another important issue. Some power strips have surge protection built-in, some don’t. With the money you’ve invested in your equipment, you’ll want to make sure it’s protected. Any mission-critical equipment should be connected to a rack-mounted uninterruptible power supply (UPS) and a power distribution unit to remotely control and reboot power.
Next you need to select the appropriate accessories. The first, and most important, is cable management. Many racks have built-in cable management troughs and cable rings for routing cable. If your rack doesn't have these, consider adding managers for neatly routing cable. Vertical managers are great for organizing cable runs top to bottom. Horizontal managers are designed to guide cables and hold them precisely at the same level as mounted equipment. You can also add inexpensive hook-and-loop cable ties to hold and bundle cable securely.
For high-density applications, there are specially designed cable managers that handle large amounts of cables. These systems have oversized channels with molded fingers that guide wiring to mounted devices at precise increments while maintaining the proper bend radius for the cable. They also have covers that you can remove completely for faster cable installation.
Consider shelving for your rack. The type you choose depends on the equipment you plan to mount. You can choose from solid or vented shelves, stationary or pull-out shelves. There there are shelves built to hold specific pieces of equipment such as servers, monitors, and keyboards. You can place small devices on a cantilevered shelf. Larger, heavier items, such as monitors, should be put on a center-weight shelf. There are even panels designed to hold flat-screen monitors.
Other accessories include rackmount fan trays and filler panels, which can be vented or nonvented. Also, don’t forget grounding bars to ground the rack and the equipment in it.
