WATCH THE PRESENTATIONCGG installed its first rack of oil immersion cooled compute systems in June 2011. A variety of lessons have been learned in that time. This presentation covers some of those lessons including: actual cost savings (CapEx, OpEx), equipment failure rates, thermal performance, and operational issues. The presentation begins with an outline of the specific business scenario that led to considering oil immersion cooling. It closes with an outline of possible next steps and remaining hurdles. Before going into those details, our current thinking on the feasibility of oil immersion cooling can be summarized as follows
• Oil immersion cooling provides significant ROI on a case by case basis depending on the specific business scenario.
• CapEx savings are realized as ‘deferring’ expenditures for a number of years.
• OpEx power savings are approximately 30% for standard high density air cooled servers.
• Our current oil immersion datacenter has an ‘Equivalent PUE’ of 1.05.
• There are specific equipment failure modes and drawbacks to oil immersion but these can be dealt with successfully.
• Significant additional savings remain to be exploited.
Business Scenario
The business scenario involved upgrading a PUE ~ 2 legacy datacenter. An upgrade to high efficiency air cooling and conversion to oil cooling were evaluated. Oil was chosen because of lower OpEx and the ability to defer CapEx.
Cost Savings
The OpEx part of cost savings comes to approximately 30% of the power consumed by air cooled equipment in high efficiency (PUE = 1.35) datacenter. The CapEx savings is significant, but because it involves NPV calculations and other business considerations, is not evaluated explicitly here.
Oil Immersion Challenges
There are unique challenges raised by oil immersion cooling. These can be dealt with successfully. They include material degradation (plastics & silicones degrade in one way or another in oil), lower equipment density, and an ‘oily’ work environment. Component failure rates are similar in oil and air.
Oil Immersion Bonuses
There are several new benefits provided by oil. Decreased sound levels and greater thermal inertia provide operational benefits. An increase in thermal headroom of 20C is observed for the hottest components.
Next Steps
There are significant opportunities arising from increased thermal headroom. A simple thermal model shows how server density can be increased and the feasibility of warm water cooling.