The term 42U is often seen when looking at full-height server cabinets. The U refers to a standard rack-unit measurement used to describe equipment height.
Equipment normally draws cool air from the cabinet front and exhausts heat at the rear. Blanking panels reduce recirculation through unused rack spaces.
What is one U?
One rack unit, written as 1U, is a standard vertical measurement used for rack-mounted equipment. Equipment is commonly described as 1U, 2U, 4U and so on.
What does 42U mean?
A 42U cabinet provides 42 rack units of vertical mounting space. That does not mean it can automatically hold any combination of equipment adding up to exactly 42U, because other physical requirements need to be considered.
Leave room for infrastructure
A rack may contain servers as well as switches, patch panels, PDUs, cable managers, shelves and other components. These all consume space or affect the layout.
Do not fill every U
Planning a rack with no spare capacity can make future expansion difficult. The amount of spare space required depends on the expected growth and the installation.
| Equipment description | Typical rack height notation |
|---|---|
| Rack-mounted equipment | Often specified in U |
| Small rack device | May be 1U |
| Larger rack device | May be 2U, 3U, 4U or more |
| Full-height cabinet | Often specified by total available U |
The actual equipment dimensions and cabinet mounting requirements should always be checked before planning a rack.
Confirm the exact product specification, supported configuration and compatibility before ordering. Platform generation, firmware, licences and optional components can change what a product supports.