Single-Phase Immersion Cooling Study of a High-Density Storage System

In this paper, a standard air-cooled high-density storage system is reengineered to demonstrate the use of single-phase immersion cooling. The storage system consists primarily of seventy-two hard drives, two single socket nodes, two SAS expander cards, NIC and a power distribution board in a 4OU form factor. It is successfully demonstrated that the storage systems can be designed to support single phase immersion cooling while supporting hot swap and cooling redundancy requirement like an air-cooled system. In an air-cooled system, temperature gradient between the drives was as high as 19°C. The drives placed at the front of the system received cooler air while the drives placed in the rear received preheated air thus resulting in a temperature gradient. The drives used for the study were 20GB Helium filled sealed drives. For immersion cooling, seventy-two drives were cooled in parallel with temperature variance of less than 3°C. The other system components such as CPU, DIMMs, SAS chip and NIC had sufficient thermal margin. It was demonstrated that the system can operate reliably for facility coolant supply temperature as high as 40°C. The resulting power consumption of the pump was less than five percent of the total IT power. In addition, the proposed cooling solution may help mitigate acoustic vibrational issues for drives often encountered in air-cooling solution. The solution is virtually silent in operation.