A content transfer method of a content transfer system comprising a plurality of first storages for recording first contents, a second storage for recording second contents and managing said first contents, and a third storage for recording third contents,
- wherein said first storages, said second storage and said third storage are connected via a communication network, and send and receive information concerning each of said contents via the communication network,
- wherein said first storages execute:
- a step of sending identifying information for specifying a backup target content to said second storage and requesting said second storage to determine the existence of a content corresponding to said backup target content upon requesting said second storage to back up said backup target content among said first contents;
- and
- a step of transferring management information to be used for managing the backup of said backup target content to said second storage in substitute for transferring said backup target content upon receiving a reply from said second storage indicating that a content corresponding to said backup target content exists in said second contents;
- wherein said second storage executes:
- a step of determining the existence of a content corresponding to said backup target content based on identifying information, and a step of transferring the determination result to said first storages in response to the request from said first storages;
- a step of requesting said third storage to transfer a content corresponding to said backup target content upon determining that a content corresponding to said backup target content does not exist in said second contents based on identifying information of said backup target content in response to the request from said first storages;
- and
- a step of transferring a determination result indicating the existence of a content corresponding to said backup target content to said first storages on condition of receiving the transfer of a content corresponding to said backup target content from said third storage;
- wherein if said backup target content exists in said second contents and said third contents, said second storage compares a first quality of a part of said backup target content, a second quality of a part of said backup target content existing in said second contents and a third quality of a part of said backup target content existing in said third contents;
- wherein if said backup target content exists only in said second contents, said second storage compares said first quality with said second quality;
- wherein if said backup target content exists only in said third contents, said second storage compares said first quality and said third quality;
- wherein said first storages send said target content and management information to be used for managing the backup of said backup target content to said second storage if said first storages receive said determination result indicating that said backup target content does not exist in said second contents or said third contents;
- wherein said first storages send the part of said backup target content and management information to be used for managing the backup of said backup target content to said second storage if said first storages receive said determination result indicating that said second quality and said third quality are inferior to said first quality;
- wherein said first storages send said management information to be used for managing the backup of said backup target content to said second storage if said first storages receive said determination result indicating that said backup target content exists in said second contents or said third contents, and if said first quality is inferior to said second quality or said third quality;
- and
- wherein said management information to be used for managing the backup of said backup target content is configured from metadata that is associated with said backup target content.