I recently participated in a discussion on LinkedIn about the best, most energy-efficient way to control temperature: either the classic sensor in the return of each individual CRAC/CRAH or supply air either by under-floor sensors or sensors in the cold aisles.
ASHRAE is getting ready to finalize its third edition of TC 9.9. In advance of the release expected later this year, it has just published a 45-page white paper titled, “2011 Thermal Guidelines for Data Processing Environments – Expanded Data Center Classes and Usage Guidance,” which is now publicly available from ASHRAE.