The Question: We posed the following question to the audience -- Why keep servers turned on when they are not being used? This is especially impactful when you consider a recent APC white paper indicating that the average server consumes about 50% of its loaded power, even when sitting idle. The analogy is to lighting in modern office buildings, where motion sensors only turn lights on for occupied rooms... and when a room is deemed idle and unoccupied, lighting is turned off. Why couldn't the same analogy apply to the over-provisioned servers in a data center - during peak times, as well as to nights/weekends? Clearly the problem is not as simplistic as light switches, but why isn't there a solution?
The Demo: So, with 3 video projectors blazing, two live data centers on-line, and the Collage Software in control, we set out to prove to the audience that power management was not only possible, but that it would save money as well. The scenario illustrated that an external trigger (say, a "curtailment event" from a local utility) could cause Collage to apply policies to power-down low-priority servers (according to their power consumption and/or efficiency) and even migrate-away their compute loads to another data center where power was cheaper. Obviously, the same could be done on a scheduled basis as well. Well, the demo was a success, even down to watching real-time power consumption curves dip-and-settle.
Not uncoincidentally, it turns out that power companies (like PG&E here in Sunny CA) offer incentives for shifting power to off-peak times, as well as special demand-response programs and incentives for firms that react to electrical demand during "events" by additional short-term reductions in power use (like turning off lights & HVAC). Our initial conversations with PG&E (who was also in the room!) showed that they were eager to pursue this type of approach, and confirmed that Cassatt was the first to tackle this problem!
The Numbers: Following the demonstration, we also ran some conservative financial numbers. They showed that a company with 500 typical servers could regularly schedule shut-downs of idle equipment -- even during peak periods as well as nights/weekends -- and save 20% + of their total energy costs! These indications were significantly encouraging regarding the economics of this approach.
The Punchline: So, what there was to take away here is that medium-to-large data centers can save a bunch of $, be "green", and do so without having to change any hardware or software! So ask yourself -- as you pursue installation of energy-efficient IT *equipment* why are you not also pursuing energy-efficient *operation* of that equipment??
My Related Blogs:
4/6/07 - D'oh: Turning Off Idle Servers
1/22/07 - Clothes Driers, Data Centers, and Power Management