VIRTUALISATION TURNS UP HEAT ON DATA CENTRE CONTRACTORS Andrew Kirker, General Manager - Datacentres
Squeezing energy efficiencies out of modern data centres can create unintended hot spot issues.
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irtualisation was seen as the great energy saver in the data centre, yet for electrical contractors it has thrown up an unexpected problem — electrical and cooling hot spots. Hot spots occur when servers are installed and grouped in high-density configurations, and when an unexpected computation load is placed on specific needs. While temperature management and physical server configuration is a core focus for data centre managers, minimising hot spots has profound implications for electrical contractors. Increased likelihood of branch circuit overload, unforeseen stresses on energy redundancy systems and increased power for cooling systems all need to be considered before rolling out a data centre refresh. Because of these concerns electrical contractors need to work very closely with data centre managers when undertaking a new install or significant refresh. Electrical contractors need to be aware of the problems and the energy mitigation strategies that are critical in dealing with hot spots in a virtualised server environment.
The rise of high density While virtualisation may reduce overall power consumption in the room, virtualised servers tend to be installed and grouped in ways that create localised high-density areas that can lead to ‘hot spots’. This cooling challenge may come as a surprise to some given the dramatic decrease in power consumption possible today. However, as
12 ECD [ELECTRICAL+COMMS+DATA] - MAY/JUNE 2017
a physical host is loaded up with more and more virtual machines its CPU utilisation and power draw increases. Virtualised machines (VMs) also require more processor and memory resources, which again increase power consumption. The solution: If an existing cooling infrastructure is not sufficient for a high-density environment, there are a few approaches that can be applied. One of the most common is to simply ‘spread out’ the high-density equipment throughout the data centre floor rather than grouping it altogether. This approach does have its drawbacks though, including increased floor space consumption and higher cabling costs. A more efficient approach may be to isolate higher density equipment in a separate location from lower density equipment. This would involve consolidating all high-density systems down to a single rack or row(s) of racks. Dedicated cooling air distribution, row cooling and/or air containment could then be brought to these isolated high-density pods to ensure they receive the predictable cooling needed at any given time. This approach enables maximum density per rack and also offers a solution for organisations that require high-density equipment to remain co-located.
The impact on power usage effectiveness (PUE) A widely touted benefit of virtualisation has been reduced energy use and costs as a result of physical server consolidation. And,
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