What Is a Server Rack? Racks, Cabinets and What Goes Inside
A server rack is a standardised steel frame that holds servers, network switches, patch panels and power equipment in a fixed, organised stack. Almost every server room, comms room and data centre is built around racks, because they keep equipment secure, cooled, powered and easy to cable.
What is a server rack?
Server racks follow the 19-inch standard: equipment panels are 19 inches (482.6 mm) wide and bolt to vertical mounting rails with a fixed hole pattern. Height is measured in rack units (U); one rack unit is 1.75 inches (44.45 mm). A 1U switch takes one unit, a 2U server takes two, and a 42U rack offers 42 units of mounting space.
Server rack or server cabinet?
The terms are often used for the same thing. Strictly, a rack can be an open frame, while a cabinet is an enclosed rack with doors, side panels and a roof. Cabinets add security, dust protection and controlled airflow; open-frame racks give faster cable access in rooms that are already secure.
| Type | Typical sizes | Best for |
|---|---|---|
| Wall-mount cabinet | 6U to 18U | Small comms rooms, CCTV, FTTH points |
| Floor-standing cabinet | 22U to 47U | Server rooms, main distribution frames |
| Open-frame rack | 42U to 47U | Secure rooms needing quick cable access |
What is inside a server rack?
- Servers and storage, usually deep rack-mount units
- Network switches and routers
- Copper and fibre patch panels where the cabling terminates
- Cable managers to route patch cords
- Rack PDUs and often a UPS for power
- Shelves for non-rack equipment, blanking panels and cooling fans
Choosing size, width and depth
Add up the rack units of everything you will install, then leave 30 to 50 per cent spare for growth. 600 mm wide frames suit patching; 800 mm wide frames leave room for vertical cable management. Servers usually need 800 mm or 1000 mm depth, while patching-only cabinets can be shallower. Check the load rating against the weight of the equipment, and earth the rack and all metal parts.
Airflow and cooling
Most rack equipment draws cool air in at the front and exhausts warm air at the back. Keep that front-to-back flow by fitting blanking panels in empty spaces, using perforated doors where heat load is high, and adding roof fans where needed. See our network cabinet sizing guide for detailed planning.
FAQ
What is a rack mount server?
A server built in a flat 19-inch chassis, one or more U high, that bolts into a rack instead of standing alone as a tower.
How tall is a 42U rack?
42U of mounting space is 1,867 mm (42 × 44.45 mm); the cabinet itself is taller once the base and roof are added, typically around 2 m.
Do I need a server rack for a small network?
A small wall-mount cabinet of 6U to 12U is enough for a switch, a patch panel and a router, and keeps them secure and tidy.
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