What Is a Computer Rack or Server Rack?

A computer or server rack is a standardized frame or enclosure designed to mount multiple electronic equipment modules. Each module has a front panel 19 inches (48.26 cm) wide, including edges or ears that protrude on each side, allowing it to be fastened to the rack frame with screws.

Racks are essential in data centers, server rooms, and for any organization that requires multiple servers, networking devices, UPS systems, and other IT equipment to be organized in a compact, efficient, and accessible manner. The standard rack size enables different devices from various manufacturers to be securely mounted together, simplifying cabling, cooling, and maintenance.

What Is a Computer (Server Rack) Used For?

A computer/server rack is used in various settings, including data centers, telecommunications rooms, and IT environments. These functions include:

Organization. Racks enable the neat arrangement of servers, network devices, UPS systems, and other IT equipment. Efficiently using space and keeping the environment organized provides easy access for maintenance and component upgrade purposes.
Standardization. The standardized dimensions of rack units (RUs) ensure compatibility with various manufacturers' different types of equipment. Standardization simplifies the process of configuring and scaling IT infrastructures.
Cooling and ventilation. Electronic equipment needs proper airflow to perform optimally. Racks are designed to support efficient cooling and ventilation by using fans, dedicated cooling systems, and strategic placement that facilitates airflow.

Cable management. With the concentration of multiple devices within a rack, managing power and network cables becomes essential to maintain order and accessibility. Racks often incorporate cable management systems to keep cables organized, protected, and out of the way.
Security. Racks provide secure enclosures to protect sensitive equipment from unauthorized access, physical damage, and environmental hazards. Many racks come with locking mechanisms that serve as the first line of defense against physical threats.
Mobility. Some racks are equipped with wheels, which makes it easier to move equipment as needed for maintenance, reorganization, or relocation within a building.
Accessibility. Racks provide easy access to the mounted equipment for maintenance, monitoring, and troubleshooting. Rack design usually includes removable side panels, doors, and mounting rails.
Power distribution. Racks integrate power distribution units (PDUs) to efficiently supply power to the mounted equipment. They often include power redundancy options to ensure a reliable power supply in the case of a single power source failure.
Environmental monitoring. Advanced racks include features for environmental monitoring, such as temperature and humidity sensors, helping to maintain optimal conditions for equipment operation and alerting administrators to potential problems.

What Is a Rack Cabinet?

A rack cabinet, also known as a server cabinet or network cabinet, is an enclosure that houses server, networking, and IT equipment in a standardized frame, similar to a computer or server rack. Rack cabinets have doors and side panels to enclose the equipment, unlike open racks, which are simply frames. This enclosure offers enhanced security and protection for the equipment while supporting efficient organization, power distribution, cooling, and cable management.

What Is “U” Space?

A "U" space, also known as a rack unit, is a standard measurement used to describe the height of equipment intended for mounting in a rack frame, such as in a server rack or network rack. One rack unit or “U” equals 1.75 inches or 44.45 mm.

The "U" sizing system allows for the uniform configuration of rack-mounted equipment across different manufacturers and setups, facilitating compatibility and efficient use of space. Equipment designed to be rack-mounted is typically described in terms of its height in “U” space. This system helps plan and allocate space within a rack, enabling administrators and IT professionals to efficiently organize and optimize their data centers, server rooms, or IT closets.

Server Rack Components

Server racks are composed of several vital components that work together to house, organize, and protect server and networking equipment, including:

Frame. The frame is the backbone of the server rack, providing the structural support for mounting all the equipment. It usually includes four vertical posts and horizontal supports, defining the rack's height, width, and depth.

Rails and mounting hardware. Rails are metal bars that attach to the vertical posts of the rack, providing the slots or holes where equipment is secured using screws or other mounting hardware. They are adjustable to accommodate different sizes of equipment.
Shelves. Not all equipment is designed for direct attachment to the rack frame. Shelves provide a flat surface for such equipment to sit on, allowing for the integration of non-rack-mountable devices.
Cable management system. These systems include rings, ducts, and trays that guide and organize cables (power, network, etc.) so they are neatly arranged and accessible, reducing clutter and optimizing airflow.
Cooling systems. Effective cooling is vital to prevent equipment from overheating. Cooling includes built-in fans, vented panels, and air conditioning units specifically designed for racks. Some advanced setups also use liquid cooling systems.
Power Distribution Units (PDUs). PDUs distribute electrical power to the equipment in the rack. They include multiple outlets and provide surge protection, remote monitoring, and control of power to individual outlets.
Blanking panels (filler panels). These are flat plates that fit into unused rack spaces to improve airflow and maintain proper cooling by directing air through the rack in a controlled manner, rather than letting it pass through empty spaces.
Doors and side panels. In enclosed racks, doors and side panels protect equipment from dust, unauthorized access, and physical damage. They also contribute to airflow management and noise reduction. Doors may be perforated or equipped with glass windows for visibility.
Wheels/casters. Some racks come with wheels or casters to make them mobile, which allows easier movement within a data center or IT room.
Security features. These include locking doors, side panels, and other mechanisms designed to prevent unauthorized access to the sensitive equipment housed within the rack.
Environmental monitoring equipment. Advanced server racks may include sensors and monitors to track conditions like temperature, humidity, and airflow within the rack. This data is crucial for maintaining optimal operating conditions and preventing equipment failure.

Server Rack Configuration Best Practices

Here are some server rack configuration best practices:

Plan for future expansion. Allocate space for future growth to avoid overcrowding and the need for reconfiguration when adding new equipment. Future planning should include both physical space and power requirements.
Ensure proper airflow for cooling. Follow the manufacturer’s instructions for cooling to prevent overheating. Most server equipment is designed for front-to-back airflow. Use blanking panels to fill unused spaces and direct airflow effectively, and position equipment to avoid blocking air circulation.
Use efficient cable management. Organize cables using horizontal and vertical cable managers to keep them neat, accessible, and protected. Proper cable management improves airflow, simplifies maintenance, and enhances the tidiness of the rack.
Adhere to weight limits. Know the weight limits of both the rack and the floor it stands on. Heavier equipment should be placed at the bottom of the rack to lower the center of gravity and reduce the risk of tipping.
Balance the power load. Distribute power loads evenly across available circuits to prevent overloading and ensure redundant power sources are not compromised. Use power distribution units (PDUs) wisely to manage and monitor power consumption.
Label everything. Clearly label cables, equipment, and PDUs to simplify troubleshooting, maintenance, and upgrades. Accurate labeling saves time during critical situations or when performing routine tasks.
Implement security measures. Secure sensitive equipment with locking mechanisms. Consider additional security measures like surveillance cameras or restricted access to the server room for enhanced protection.
Optimize rack layout. To maximize cooling efficiency, position racks in a hot aisle/cold aisle configuration. This arrangement aligns racks in alternating rows, with cold air intakes facing one aisle (cold aisle) and hot air exhausts facing the opposite direction (hot aisle).

Monitor environmental conditions. Use environmental monitoring tools to keep track of temperature, humidity, and airflow within the rack. Adjust cooling and airflow as necessary to maintain optimal conditions and prevent equipment failure.
Perform regular maintenance and inspection. Schedule regular inspections and maintenance to ensure that all components are functioning correctly, firmware is up to date, and there are no signs of wear or potential failure. Keep the rack and equipment clean and dust-free.
Utilize vertical space efficiently. Maximize the use of available vertical space within the rack, remembering the need for proper airflow and ease of access for maintenance. Vertical PDUs and zero-U accessory mounting options help free up space.
Consider noise reduction. If the server rack is located near workspaces, use noise-reducing features like acoustic dampening panels to minimize disturbance to staff.