What is the physical layout of the data center room?

Well, data center can occupy one room of a building, one or more floors, or an entire building. Most of the equipment is often in the form of servers racked up into 19 inch rack cabinets, which are usually placed in single rows forming corridors between them.
Servers differ greatly in size from 1U servers to huge storage silos which occupy many tiles on the floor. This allows people access to the front and rear of each cabinet. Some equipment such as mainframe computers and storage devices are often as big as the racks themselves, and are placed alongside them.

1U represents one rack unit of space. A Rack Unit is 1.75 inches in height (44.49 mm).