CoolDC: A Cost-Effective Immersion-Cooled Datacenter with Workload-Aware Temperature Scaling

For datacenter architects, it is the most important goal to minimize the datacenter's total cost of ownership for the target performance (i.e., TCO/performance). As the major component of a datacenter is a server farm, the most effective way of reducing TCO/performance is to improve the server's performance and power efficiency. To achieve the goal, we claim that it is highly promising to reduce each server's temperature to its most cost-effective point (or temperature scaling). In this article, we propose CoolDC, a novel and immediately applicable low-temperature cooling method to minimize the datacenter's TCO. The key idea is to find and apply the most cost-effective sub-freezing temperature to target servers and workloads. For that purpose, we first apply the immersion cooling method to the entire servers to maintain a stable low temperature with little extra cooling and maintenance costs. Second, we define the TCO-optimal temperature for datacenter operation (e.g., 248K 273K (-25 degrees C 0 degrees C)) by carefully estimating all the costs and benefits at low temperatures. Finally, we propose CoolDC, our immersion-cooling datacenter architecture to run every workload at its own TCO-optimal temperature. By incorporating our lowtemperature workload-aware temperature scaling, CoolDC achieves 12.7% and 13.4% lower TCO/performance than the conventional air-cooled and immersion-cooled datacenters, respectively, without any modification to existing computers.