Metrics & Measurements

power utilization density and sanity

If ASHRAE wants to make a real contribution to data center design it should set standards for recommended maximum power density limits for air cooled IT equipment. While increasing the number of transistors on a chip to whatever degree is possible may be desirable, increasing the power consumed per rack by increasing the number of blade servers you can squeeze in as power consumption of per server increases has created horrendous problems for air conditinging and power engineers. As it is, not only microclimate within areas of a data center but microclimate within each rack is now an issue. The requirement to condense AC equipment the point where it must be installed in each rack reduces the ability to provide redundancy and eliminates the abiltiy to achieve compartmentalization, two of the essential factors required for reliability as explained in Uptime Institute's Tier four criteria. In mission critical applications reliability must trump efficiency because data center failure can equal business failure. In-rack cooling resulting in reducing or eliminating the huge reservoir of cold air and cold manonary in a raised floor plenum means that the available response time for plant personnel to respond to HVAC emergencies is reduced from up to 15 to 30 minutes to zero. Increasing the acceptable operating temperature of the data center to increase PUE merely increases the likelihood of IT failure and reduces the time it will take to occur after an HVAC failure event. Greater efficiency results from better envelope thermal insulation, not trick metrics ignoring the facts of thermodynamics and ill conceived tradeoffs to cut utility costs.

Posted at 10:55 AM on December 08, 2011 by Mark