“A thorough consideration of the function of a Datacentre is essential for effective design. The flooring, cooling, power, cabling, racking, containment, lighting and security requirements – and how these fit together – all need to be communicated, understood and planned by all trades and stake holders before the build begins. In this way, there is potential to make Datacentres that are cost-effective to run without sacrificing capacity. Unfortunately this planning very rarely happens, so the problems usually start before the first floor tile is laid.”
Every Datacentre manager wants to optimise power and cooling capacity, and increase server and rack density. The more racks that are available for the storage of IT equipment, the greater the revenue is for the Datacentre. However, this needs to be balanced with the need for cooling the equipment and the function of the Datacentre. The IT industry consumes 3.3% of Britain’s total grid power and now accounts for an equivalent level of CO2 emissions to aviation. A staggering 60% of this could be on cooling.
A skilled designer should be able to produce an efficient Datacentre and drastically reduce energy requirements, while still increasing capacity and maximising function.
If the Datacentre is designed with the above knowledge and an understanding of airflow management then the need for expensively-cooled air can be reduced. For much of the year in Northern Europe the outside temperature is low enough to provide free cooling. Using naturally-cooled air can increase power usage effectiveness.
A common mechanism of cooling is to have a raised floor. Cool air flows under this floor and then into the Datacentre through ventilation tiles. These tiles must be carefully placed and balanced to feed cool air into the aisles and servers.
A holistic approach to the design is essential. Jeremy says, “If each contractor sees their job in isolation then problems will emerge. For example ventilation tiles laid just 50 mm away from the architect’s expected location because the contractor wants a straight edge throws the whole plan into chaos because they won’t line up with the racks, cableways, secure-area cage walls etc. Such problems occur because individuals don’t have an overview of how their work interacts with the rest of the design.
In an office, desks can be moved to access a power supply, but in Datacentres the position of the racks is critical and is fixed. A key issue is that power and cooling are often planned per square metre, whereas the power and cooling requirements are per rack. There is often considerable variation in power and cooling usage across the floor. Dataracks advises that power and cooling should be introduced into the Datacentre in a modular format because this allows flexibility to adjust the services according to rack density.
Jeremy describes a recent Datacentre design and build project which illustrates why needs such as power and cooling must be considered simultaneously. “Over the whole floor there was sufficient power and cooling for 520 racks at 4 KWs per rack, with the aim of providing as many racks as possible per square metre of floor. However, the design only allowed for 330-vented tiles with an aisle width of 900 mm. The layout meant that some racks simply couldn’t be supplied with enough cooling, yet in other parts of the centre cooling was underutilised. The perimeter layout of the computer room air conditioning (CRAC) units meant that the underutilised cooling could not flow freely in the room. This came to light when we measured up for the racks, cold-aisle containment and overhead cableway, yet a pre-installation meeting could easily have prevented this.”
It is imperative that the architect works closely with the installers of power, cooling and networks to identify exactly where cables are required. The cables should drop down or rise neatly through the holes in the cabinet or floor tiles. If cables are just a few centimetres out then new holes may have to be drilled in the floor tile or the entry in the rack cabinets. But these hours of work can be avoided with a bit of forethought and an awareness of function.
When designing a managed service centre there are even more issues that an architect must consider. In such Datacentres, facilities are provided for clients to bring their own hardware and racking. This could be a shared area or a dedicated suite.
“A common problem is that different tenants want to use different racks, which don’t butt up tightly together. The standard measurements relate to the rack mounting inside the cabinet, but the outer measurements can vary considerably. Using a standard rack throughout the Datacentre helps overcomes this problem.
“If all parties had visibility of the design and understanding of the function prior to the build, this would not only ensure that the installation was faster but it would reduce unnecessary wastage and increase capacity and income in the Datacentre. A meeting beforehand may even discover that a plan won’t work!”
Dataracks has produced a 10-point guide to improving Datacentre design, specifying equipment and reducing running costs.
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