When you tune your server for energy savings, you must consider performance as well. Tuning affects both performance and power, sometimes in disproportionate amounts. For each possible adjustment, consider your power budget and performance goals to determine whether the trade-off is acceptable.
You can calculate your server's energy efficiency ratio for a useful metric that incorporates both power and performance information. Energy efficiency is the ratio of work that is done to the average power that is required during a specified amount of time. In equation form:
You can use this metric to set practical goals that respect the tradeoff between power and performance. In contrast, a goal of 10 percent energy savings across the datacenter fails to capture the corresponding effects on performance and vice versa. Similarly, if you tune your server to increase performance by 5 percent and that results in 10 percent higher energy consumption; the total result might or might not be acceptable for your business goals. The energy efficiency metric allows for more informed decision making than power or performance metrics alone.
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