Controller to Regulate Maximum Server CPU Temperatures in a Rack by Varying CRAC Supply Air Temperatures

Conventionally, raised floor data centers operate using controllers that only maintain constant data center space conditions (i.e. supply air temperatures or return air temperatures) at the Computer Room Air Conditioning (CRAC) Unit level with the intention of providing enough cooling for the servers. The objective of this paper is to explore the framework required to design a controller that regulates server CPU temperatures by specifying the supply air temperature of the CRAC. The controller will be an addition to the existing controller used by the CRAC to regulate supply air temperatures. In the discrete-time domain, implementation and the performance of the modified integral action controller is analyzed and other important parameters are compared. As a preliminary attempt, the controller will be designed for a standard 44U cabinet with 42 “1U” servers, where the machines will execute a prescribed compute load variation: (1) step increase in all compute loads and (2) scaled down representation for a rack of servers using utilization trends from one of Google’s data centers. Ultimately, the development of this controller is motivated by the growing interest in Data Center Infrastructure Management (DCIM) where the IT level and facility level information are both used to intelligently plan and manage resources of a data center.