While numerous power optimization techniques have been at all levels of design process abstractions for electronic components, until now, power minimization in mixed mechanical-electronic subsystems, such as disks, has not been addressed. We propose a conceptually simple, but realistic power consumption model for disk drives. The core of the paper are heuristics for optimization of power consumption in several common hard real-time disk-based design systems. We show how to coordinate tasks scheduling and their disk data assignment, in order to minimize power consumption in both electronic and mechanical components of used disks. Extensive experimental results indicate significant power reduction.