CurtMonash writes "Parallel Efficiency is a simple metric that divides the actual work your parallel CPUs do by the sum of their total capacity. If you can get your parallel efficiency up, it's like getting free servers, free floor space, and some free power as well. eBay reports that it amazed even itself by increasing overall PE from 50% to 80% in about 6 months — across tens of thousands of servers. The secret sauce was data warehouse-based analytics. I.e., eBay instrumented its own network to do minute-by-minute status checks, then crunched the resulting data to find bottlenecks that needed removing. Obviously, savings are in the many millions of dollars. eBay has been offering some glimpses into its analytic efforts this year, and the PE savings are one of the most concrete examples they're offering to validate all this analytic cleverness."