Patent ID: 8612715

Claim:
A storage system being coupled communicatively to an external device and providing a storage area to be used by the external device, comprising: a plurality of storage apparatuses of different performance capabilities, each having a storage medium that provides the storage area; and a storage controller configured to control a use capacity of each of the storage apparatuses for each user using the storage system, the storage controller including: a storage part; a de-duplication part; and a use capacity checking part, wherein the storage part stores available space amount information indicating an available space amount of the storage area of each of the storage apparatuses, ideal utilization information indicating ideal utilization of the storage area of each of the storage apparatuses by each user, the ideal utilization information being used for limiting utilization of the storage area of each of the storage apparatuses by each user, and actual utilization information indicating actual utilization of the storage areas of each of the storage apparatuses by each user, wherein the de-duplication part is configured to determine whether or not a plurality of pieces of identical data are stored in the respective storage apparatuses, when it is determined that a plurality of pieces of identical data are stored in one or more of the storage apparatuses, deletes the pieces of identical data except meta data of the identical data and any one of the pieces of the identical data, and changes the available space amount information of the storage apparatus that has stored the pieces of identical data as deleted, wherein the use capacity checking part is configured to determine whether or not the actual utilization exceeds the available space amount or the ideal utilization for each of the storage apparatuses based on the available space amount information, the ideal utilization information and the actual utilization information, when the actual utilization in any of the storage apparatus exceeds the available space amount or the ideal utilization, migrates at least a part of the data stored in the storage apparatus as determined to another storage apparatus, and changes the available space amount information and the actual utilization information of the storage apparatus from which the data are migrated and the storage apparatus to which the data are migrated.