Global Fan Speed Control Considering Non-Ideal Temperature Measurements in Enterprise Servers
Time lag and quantization in temperature sensors in enterprise servers lead to stability concerns on existing variable fan speed control schemes. Stability challenges become further aggravated when multiple local controllers are running together with the fan control scheme. In this paper, we present a global control scheme which tackles the concerns on the stability of enterprise servers while reducing the performance degradation caused by the variable fan speed control scheme. We first present a stable fan speed control scheme based on the Proportional-Integral-Derivative (PID) controller by adaptively adjusting the PID parameters according to the operating fan speed and eliminating the fan speed oscillation caused by temperature quantization. Then, we present a global control scheme which coordinates control actions among multiple local controllers. In addition, it guarantees the server stability while minimizing the overall performance degradation. We validated the proposed control scheme using a presently shipping commercial enterprise server. Our experimental results show that the proposed fan control scheme is stable under the non-ideal temperature measurement system (10 sec in time lag and 1C in quantization figures). Furthermore, the global control scheme enables to run multiple local controllers in a stable manner while reducing the performance degradation up to 19.2% compared to conventional coordination schemes with 19.1% savings in power consumption.