Establishing a Floor Plan for a Data Centre

A floor plan strongly affects the power density capability and electrical efficiency of a data centre. Despite this critical role in data centre design, many floor plans are established through incremental deployment without a central plan. Once a poor floor plan has been deployed, it is often difficult or impossible to recover the resulting loss of performance.

A data centre floor plan includes the layout of the boundaries of the room (or rooms) and the layout of IT equipment within the room. Most users do not understand how critical the floor layout is to the performance of a data centre, or they only understand its importance after a poor layout has compromised the deployment. The floor plan either determines or strongly affects the following characteristics of a data centre:

• The number of rack locations that are possible in the room
• The achievable power density
• The complexity of the power and cooling distribution systems
• The predictability of temperature distribution in the room
• The electrical power consumption of the data centre

Many users do not appreciate these effects during data centre planning, and do not establish the floor layout early enough. As a result, many data centres unnecessarily provide suboptimal performance.

Floor plans must be considered and developed at the appropriate point in the data centre design process. Considering floor plans during the detailed design phase is typical, but simply too late in the process.  Floor plans should instead be considered to be part of the preliminary specification and determined BEFORE detailed design begins.

It is not necessary for a floor layout to comprehend the exact location of specific IT devices. Effective floor plans only need to consider the location of equipment racks or other cabinets, and to target power densities. These preliminary floor layouts do not require knowledge of specific IT equipment.

For most users it is futile to attempt to specify particular IT equipment locations in advance – in fact, racks may ultimately house equipment that is not even available on the market at the time the data centre is designed.

The reasons that floor plans must be considered early, as part of the preliminary specification, and not left until the later detailed design include:

• Density is best specified at the row level, so rows must be identified before a density specification can be created.
• Phasing plans are best specified using rows or groups of rows, so rows must be identified before an effective phasing plan can be created.
• The floor grid for a raised floor and the ceiling grid for a suspended ceiling should be aligned to the rack enclosures, so rows must be identified before those grids can be located.
• Criticality or availability can (optionally) be specified differently for different zones of the data centre –  rows must be identified before a multi-tier criticality plan can be created.

Density and phasing plans are a key part of any data centre project specification, and both require a row layout. Detailed design can only commence after density, phasing, and criticality have been specified.

Therefore, a floor plan must be established early in the specification phase of a project, after SYSTEM CONCEPT but well before DETAILED DESIGN.