In a storage system having a function of acquiring update history information in correspondence with a write operation from a host, update data according to the amount of data written will become enormous. Thus, there is a problem in that long-term backup and data management using update history information is not possible. A management computer defines a service level according to time progress of data, and stores and manages update history information according to the service level in the respective stages. The management computer manages the update history Information, and partially migrates update data from a certain storage system to another storage system according to the service level required in the data. The management computer also restores data in the storage system to which the update data was migrated.