System and method for automated page-based management in storage systems. The system includes host computers, file servers and a storage system having automated page-based management means. The storage system interface receives instructions to change the condition for decision for migration regarding particular parts or the whole volume. The host computer can control execution of the migration performed by the storage system by specifying areas or volumes with the condition via the interface. Highly optimized, appropriate data placement and data relocation in computer system can be achieved when the application, host computer or management computer can recognize or predict the usage of the data or files. The storage system having automated page-based management may include compression/decompression and a control method for the compression and decompression process.