Method for saving power in a system by placing inactive computing devices in optimized configuration corresponding to a specific constraint

A method for managing power consumption in a system including computing devices in both active and one or more inactive states of readiness, the method comprising:

• receiving, at a processing unit, a request to one of:
• activate or deactivate one or more computing devices from a respective group of inactive or active computing devices, each said inactive or active computing device initially in a pre-determined state of readiness;
• activating or deactivating said one or more computing devices, said activating or deactivating resulting in a number of computing devices in one or more states of readiness i;
• computing an optimal configuration of said computing devices in said one or more said states of readiness i by minimizing an expected power consumption Σi Ai Pi where i represents all inactive computing device states, Ai represents a number of said computing devices currently in each state i, and, P, represents an average power consumption of computing devices while in said state i;
• and,
• placing said computing devices in said optimized configuration,
• formulating an objective function to be minimized, said objective function representing said expected power consumption Σi Ai Pi subject to a constraint,
• wherein, after one of said activating or deactivating one or more computing devices:
• computing a resulting activation vector A′ representing said resulting number of computing devices in one or more activation states of readiness i;
• and
• computing an activation vector A″ representing a number of computing devices in said optimized one or more activation states of readiness i;
• wherein said objective function is subject to a constraint that Rk≦R0k for each computing devices k, wherein said R represents a readiness vector, a kth component Rk representing a minimal amount of time for k computing devices to be restored to an active state given a specific activation vector A and a transition latency matrix T;
• and, R0 represents a specified readiness vector, a kth component R0k representing a specified constraint on a maximum time permitted for k inactive servers to be restored to said active state,
• wherein a program using said processor unit is configured to perform one or more of said receiving, activating, computing, placing, formulating and said computing said activation vectors A′ and A″.