This is the forth article in a series on DCK Executive Guide to Data Center Designs.
Historically, data center IT loads have been relatively stable and predictable if viewed over a 24 hour or weekly period. This is beginning to change for several reasons. The first is virtualization, which originally allowed for individual applications which were running on distributed and underutilized servers, to be consolidated on to more centralized hardware resources such as bladeservers, resulting in higher CPU and overall server utilization, contained in less space. More advanced virtualization software offers energy management features which can monitor computing demands. Excess resource capacity such as un-utilized servers can be put into low power sleep modes or even be powered off automatically when not needed, but which would power up and then be put back on-line as computing demands rise.
The second reason is that the IT hardware itself became dynamic while becoming more energy efficient. Instead of wasting substantial amount of power when idle, they now reduce power significantly when idle, yet draw more power (and generated more heat) when called upon to do work. The US EPA Energy Star program for data center equipment requires this for Energy Star certification of IT equipment such as servers, since 2009 and now is in the process of finalizing the standards for Storage and Network equipment. (see part 3 Energy Efficiency)
The result is twofold; the overall total IT power and cooling load has begun to vary more over time as the amount of computing load increased and decreased over a 24 hour cycle. Moreover, the heat IT loads have begun to shift from rack -to-rack and row-to-row, in response to demand driven computing activity, creating traveling hot-spots across the data center.
While the overall goal is to improve the energy efficiency of the IT systems, this has challenged a lot of older more traditional cooling system which were not designed to handle these new more dynamic conditions. When considering a new data center design, the IT team needs to work with the facility design team to provide more information on the type of hardware they plan on using, as well as any of the energy management features of the virtualization software, which can impact the design of the cooling system.
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