1. A method of allocating control of virtual storage segments in a storage system among a plurality of controllers, the storage system being arranged as multiple sets of associated controllers and storage devices, the method comprising: determining performance demand among a plurality of storage device groups; distributing performance demand values according to controller processor utilization of the individual storage device groups and bandwidth utilization pro-ratable among storage device groups within a set; and associating the plurality of storage device groups with controllers based on the performance demand value distributions.