Define data centres in terms of power usage - not floor space

A lot of people who work in the data centre industry have allowed themselves to develop a bad habit - they think like real estate agents. But this bad habit can be broken, and we don’t need nicotine patches or hypnosis to do so. All we need is to do stop thinking about data centres in real estate terms.

Why is it that most of the people who are involved with data centres constantly talk about the industry using ‘real estate’ jargon? These people have developed the bad habit of talking about data centres, first and foremost, in terms of floor space - ‘square footage’ or ‘square meterage’, depending on your preference. It is a habit worth breaking because it will help to avoid many of the common mistakes that are made in data centres. And these mistakes can consume excessive energy that can potentially cost data centre operators vast sums of money, as well as shorten the life of equipment that is critical to the successful functioning of a data centre.

Yes, we all agree that data centre facilities are contained in buildings and that buildings are real estate. And a defining characteristic of a building is floor space - or ‘square meterage’ - the universal language of real estate. So it is no surprise that the first metric that many people typically throw around when talking about data centre projects is ‘square meterage’. But we have to remember that data centres are different to your average commercial building. They don’t function like a conventional office, warehouse, factory or residence, where floor space is the critical quantitative measurement that drives everything in the process from design to construction, to the lease or sale. It must be clearly understood that the lifeblood of a data centre is power, and the conversations that people have about aspects of a data centre need to start and end with that, or a data centre project can go horribly astray.

Power - the real characteristic of a data centre

In today’s high-density computing environments, power is the real determinate of data centre requirements and the best mode of expressing them in terms of kW of IT load. The kW of IT load is the kW of the data centre-delivered electrical power required to drive the facility’s computing devices (servers, for example).

As a measure of the power and capacity of a data centre, the parameter of ‘kilowatts’ (kW) most directly translates into the environment that is essential to support the substantial volumes of processing power, data storage and communications speeds normally associated with data centres - things like MIPS, Gbps and terabytes. These factors are used to quantify the performance of a data centre in what it must support both now and well into in the future. Perhaps most importantly, the metric of ‘kW’ is not a customised or contrived unit of measurement. Rather, it is a standard commodity - there is no functional obsolescence of kW of IT load.

As each successive generation of computing and storage equipment improves in its energy efficiency, that is, in its processing power per kW, the data centre gets more MIPS and terabytes of storage out of the same level of kW of IT load. But from the standpoint of accuracy in usage reporting, the definition of the delivered ‘product’ never changes - nor is it subject to the need for regular reinterpretation as the performance or output of the data centre increases.

Understanding the importance of kW is essential for anyone who intends to expand the operations of their data centre over time. Viewing power requirements in terms of kW of IT load is a fundamental principle for the futureproofing of any data centre. Adopting this method of determining and expressing data centre needs requires the operator to view power requirements that are based on the footprint of all the components that will reside above the raised floor. The measure of kW of IT load can, therefore, provide a counterbalance to the tendency to overestimate the power needs due to an incorrect assumption that all components require the same level of power.

For example, a cabinet full of copper or optical-fibre patch panels and cabling obviously does not require the same level of power as a cabinet full of servers or data storage equipment. Using kW of IT load as the standard unit of quantification enables decisions to be made from a ‘dollar per kW’ perspective, and this enables operators to be sure that they are making the right decisions based upon a common base of understanding.

New charge-back system standard

Unlike the issue-bound methodologies that have characterised the basis for charge-back systems up to this time, kW of IT load offers data centres managers and CIOs, along with their organisations, an unencumbered standard for use in developing the reliable and accurate cost allocation systems that their internal customers require. The adoption of this unit as the basis for system usage measurement provides benefits including:

1. It is a clear standard - kW of IT load is a clearly defined concept that can express utilisation in a standard increment of power consumed. Its definition is unambiguous and unchanging.
2. It is easily measured - Unlike ‘artificial’ or ‘customised’ units of measurement that are typically developed to address a specific business requirement, kW of IT load is a standard unit of power consumption. As a result, its utilisation data is easily captured and measurable, regardless of application or location.
3. It simplifies the ‘pricing’ mechanism - Under traditional structures in which the basic billing unit must be constructed based on the unique requirements of the supported organisations, establishing the internal ‘price’ to be allocated has been a difficult process at best for data centre managers and CIOs. This issue is alleviated through the use of kW of IT load, as the overall costs of power usage are easily captured and indisputable. By taking the total power (expressed in kW) consumed by each department or business unit in an organisation and dividing it by the total kW of the data centre(s), you get the percentage of cost for each specific department. Let’s say, for example, department ‘A’ in an organisation uses 1000 kW of a 5000 kW data centre capacity in a given month; and the total operating costs are $1 million for the month. The chargeback amount is therefore based on the simple formula of:

Logical flow - a key benefit

Logical flow is simply a matter of mapping and understanding the daily peaks and valleys of each supported business unit or applications’ power usage. For example, at Digital Realty Trust, we have a number of financial trading platforms as part of our customer base. It would be reasonable to expect that their kW consumption is not a constant flat line across the entire day. In fact, there are four immediately identifiable and significant peak periods where usage spikes during any given day in these financial institutions:

• First thing in the morning;
• Immediately before the lunch hour;
• Immediately after the lunch hour; and
• Finally, the period just prior to the market close.

Understanding these high and low points of usage are a key benefit to a kW-based system. The ability for organisations to understand the true nature of their energy usage enables them to regulate their power consumption more effectively, to mirror their actual utilisation patterns and so reduce their overall cost of operations. If the logical flow of usage is not taken into account, then the addition of any new hardware - which invariably occurs in a data centre - can lead to unnecessary increases in power requirements or, even worse, insufficient power availability to satisfy the power needs at peak periods.

Conclusion

Human nature being what it is, habits are not always easy to break; and learning a new language is no easy feat either. But it is important for the people who work in the data centre industry to stop talking like real estate agents and use the metric that makes the most sense for data centres - kW of IT load.

*Chris Crosby is Senior Vice President at Digital Realty Trust, the world’s largest wholesale data centre provider. Digital Realty Trust’s properties contain applications and operations critical to the day-to-day operations of technology industry tenants and corporate enterprise data centre tenants.