Hybrid Cooling Technology for Large-Scale Computing Systems: From Back to the Future

A technical perspective of hybrid cooling methodology, comprised of pumped water cooling with incorporated convection air cooling, for densely packaged high performance computing systems is presented in this paper. The technology has been implemented in the Fujitsu high-end server GS8900 (released in 1999), and proposed with technical innovations for future large-scale computing systems. Design strategies of cooling systems, including water cooling modules, water flow and distribution units as well as air convection architectures, are reviewed, together with advantages and performance of the technology analyzed. Low temperature chilled water is utilized in these systems, where the system board is assembled with a liquid cooling unit on each one for cooling of major processor and supporting chips. Memory modules, other devices and components on the system board, as well as power supply units in the rack, are cooled by ambient air convection. Besides of the high cooling capability, attention is given especially to advantages of the technology with tremendously lowered power consumption, enhanced system reliability and increased packaging density, improvements in cooling efficiency and easy of serviceability are emphasized as well.