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Capacity Management and Green IT

Use capacity management to save money while optimizing your existing data center set up.
Aug 4, 2008

George Spafford


Organizations are very concerned about the environment for a variety of reasons these days. For IT, one of the challenges is that our services fundamentally need energy to operate. Literally, if we turn off the power then we shut down all the IT services. In the current socioeconomic situation of skyrocketing energy costs, concerns over global warming and the need to manage risks, IT organizations would be very well served to take a closer look at the ITIL Capacity Management process as a means to better manage energy consumption.


The idea behind the Capacity Management process is to provide computing resources to the organization in a manner that makes the business sense. The premise is very straight forward: through advance planning and monitoring of the current state (in terms of the business, IT services and IT systems), proactive decisions can be made that lead to better procurement and/or development decisions. In turn, this reduces reactive decision making that is inevitably rushed and results in suboptimal outcomes including the potential for higher costs and lower quality.


In terms of energy, it can be viewed the same as any other resource with limitations. There are limits to the power available from the utility today and limits as to what can actually get into the data center. There are also limits to growth as some groups are finding out. Their electric utilities are telling them that additional power is not available from the grid they are on.


Where It Goes


Another challenge to factor in is the IT equipment alone doesn’t account for all the power a data center uses. In fact, it is common to see the IT equipment only account for 30% of the power consumed. The other 70% goes to cooling, power infrastructure, lighting, etc. So when power is being planned for, the overall needs of the system in which the IT equipment resides must be taken into account as well.


For each watt of IT equipment added in a data center, there also will be one incremental watt of cooling needed. There needs to be sufficient cooling capacity to keep IT equipment at, or below, 72 degrees Fahrenheit to avoid heat related incidents. With today’s dense, power intensive systems maintaining an acceptable temperature can be a challenge and presents another resource constraint to manage because cooling is itself limited and it also requires electricity.


There is another important reason to manage capacity as well. In general, as the level of utilization of electrical systems goes down, so do their efficiencies. Thus, a UPS running at 50% will be less efficient than a UPS running at 90% of stated capacity. This is also true for power supplies, cooling and other systems. Traditional approaches of “over sizing” various systems to “play it safe” can result in higher energy costs and need to be replaced with more deliberate management approaches.


In response to concerns over energy consumption, groups need to review and formalize their Capacity Management process. At a policy level there needs to be guidelines and standards set forth about the organization’s direction for green IT, and expectations around energy consumption and then the process designed and implemented accordingly.


At a process level, there needs to be integration with project management, procurement and Change Management to ensure that current capacity is understood for electricity, cooling, and so forth and that the potential impacts of new or changed services are clearly understood both at the point of initial implementation and trended over time.

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