What to Consider When Choosing a Server Rack

Black Box Explains

Why Racks?

Types of Racks

What are you going to put in your rack? If you are installing patch panels, a two-post rack with cable management may be the right choice. If you have a mix of networking equipment, servers and patch panels, a four-post rack provides a stable base and four-point mounting for deeper/ heavier equipment like servers and uninterruptible power supply (UPS) units. Four-post racks with front-to-back adjustable rails are suggested for flexible mounting of both standard and extra-deep equipment.

Understanding Rack Measurements

The main component of a rack is a set of vertical rails with mounting holes that you attach your equipment or shelves to. Two-post racks typically have 12 to 24 or 10 to 32 threaded holes for quick installation of patch panels, while four-post racks usually have M6 square mounting holes for mounting servers. Since rack widths are standard, the amount of vertical space determines how much equipment can be installed.

Rack Units (Height)

The number of rack units is abbreviated as “U.” This is a measurement of the vertical space available on the rails. Cabinets, racks and rackmount equipment are all measured in rack units. One rack unit (1U) is equal to 1.75" of usable vertical space. For example, a device that’s 2U high takes up 3.5" of rack space. A rack that’s 20U high has 35" of usable vertical space.

Width between Rails

Width is commonly given in inches, measured from one mounting hole to the corresponding hole on the opposing rail. The most common rail width is 19". To rackmount smaller equipment, add rackmount adapter brackets. Legacy equipment may require 23" rails and racks.

Rack Options

Power & Surge Protection

All critical equipment should be connected to a rack-mounted UPS. A UPS prevents your equipment from crashing during a brief blackout or brownout and allows enough time to shut everything down properly in the event of an extended power outage.

Rackmount power strips and PDUs come in versions that mount either vertically or horizontally. PDU options can include "metered" to show current draw or "outlet-managed" to monitor power and provide status updates and alarms.

Cable Management

Plotting your connections in advance will help you decide the most efficient way to organize your cables. Knowing where the connections are can help determine whether it’s better to run cables horizontally or vertically.

Many racks have built-in cable management troughs and cable rings for routing cable. If your rack doesn't have built-in cable managers, they can be added to accommodate your specific needs along with inexpensive hook-and-loop cable ties to hold and bundle cable securely.

  • 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

For high-density cable management applications, there are specially designed systems with oversized channels and molded fingers. These molded fingers guide the wiring to mounted devices at precise increments while maintaining the proper bend radius for the cable. Completely removable covers allow for faster cable installation and protection.


A variety of solid, vented, stationary or pull-out shelves can make your rack configuration as efficient as possible: shelves built to hold specific pieces of equipment such as monitors and keyboards, cantilevered shelves for small items as well as center-weight shelves for larger, heavier items.

Rack-mounted panels designed to hold flat-screen monitors can be installed. Additional accessories include vented or non-vented fan trays and filler panels and grounding bars to ground the rack and the equipment in it.

If you are unsure what type of rack is best for your application, contact Black Box Tech Support at 1.877.877.2269 to speak with one of our experts. We will be glad to help you find the right enclosure for your equipment.

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