Energy consumption has become an important issue in the design of battery-operated mobile devices and sophisticated data centers. The storage hierarchy, which includes memory and disks, is a major energy consumer in such systems; especially for high-end servers at data centers. Much work has focused on energy control algorithms for storage systems that transition a device into a low power mode when a certain usage function exceeds a specified threshold. These algorithms are difficult to use in real systems, however, because designers must painstakingly and manually tune threshold values, and even then a performance guarantee is difficult. To address these limitations, we develop three algorithms: 1) a performance guarantee technique that designers can use with any underlying energy-control algorithm 2) a performance-directed control algorithm that periodically assigns a static configuration to different devices by solving an optimization problem 3) another performance-directed control algorithm that dynamically self-tunes according to an optimal set of thresholds