Storage system and data relocation control device

A storage system comprising:

• first and second storage devices, each of which includes a plurality of physical storages and a controller coupled to the plurality of physical storages, said first and second storage devices having at least one logical volume configured by at least one of the plurality of physical storages in the respective first or second storage device;
• a virtualization device adapted to be coupled to a computer system, and coupled to the first storage device via a first communication path and to the second storage device via a second communication path, said virtualization device being adapted to manage a map between the logical volumes in the first and second storage devices and at least one virtual volume constituted by at least one of the logical volumes so that the virtualization device is able to present the logical volumes in the first and second storage devices via the at least one virtual volume to the computer system;
• and
• a management device, coupled to the virtualization device, which stores volume attribute information of the logical volumes, defines storage layers each including at least two of said logical volumes of said first and second storage devices and spanning the first and second storage devices, based upon the stored volume attribute information of the logical volumes and a policy, relocates a designated source volume from an originating storage layer among the defined storage layers to a designated target storage layer among the defined storage layers with respect to the policy.