The electricity cost of cloud computing data centers, dominated by server power and cooling power, is growing rapidly. To tackle this problem, inlet air with moderate temperature and server consolidation are widely adopted. However, the benefit of these two methods is limited due to conventional air cooling system ineffectiveness caused by recirculation and low heat capacity. To address this problem, hybrid air and liquid cooling, as a practical and inexpensive approach, has been introduced. In this paper, we quantitatively analyze the impact of server consolidation and temperature of cooling water on the total electricity and server maintenance costs in hybrid cooling data centers. To minimize the total costs, we proposed to maintain sweet temperature and available sleeping time threshold (ASTT) by which a joint cost optimization can be satisfied. By using real-world traces, the potential savings of sweet temperature and ASTT are estimated to be average 23% of the total cost, while 96% requests are satisfied compared to a strategy which only reduces electricity cost. The co-optimization is extended to increase the benefit of the renewable energy, and its profit grows as more wind power is supplied.
