Method and apparatus for managing data in a multi-device data storage array. In accordance with various embodiments, a storage array of independent data storage devices are arranged to form a fast pool and a slow pool of said devices. A controller is adapted to migrate a distributed data set stored across a first plurality of said devices in the slow pool to a second plurality of said devices in the fast pool. The migration is carried out responsive to a return on investment (ROI) determination by the controller that an estimated cost of said migration will be outweighed by an overall improved data transfer capacity of the storage array over a predetermined minimum payback period of time. In some embodiments, the fast pool is formed from a plurality of solid-state drives (SSDs) and the slow pool is formed from a plurality of hard disc drives (HDD).