DATA BACKUP SYSTEM, RELAY SITE STORAGE, DATA BACKUP METHOD, AND CONTROL PROGRAM FOR RELAY SITE STORAGE

摘要

[Problem] To ensure the consistency of data at three sites including a main site while the main site is operating normally, when the main site includes a plurality of storage devices; and to ensure the consistency of data without copying all the data at the two sites other than the main site after the main site has stopped operating normally. [Solution] A data backup system is provided with: a plurality of devices for main site storage, one device for relay site storage, and one or more devices for backup site storage. While the main site is operating normally, the relay site storage implements synchronized replication of data retained by the main site storage and data retained by the relay site storage. After the main site has stopped operating normally, the data retained by the relay site storage and the data retained by the backup site storage are subjected to consistency ensuring replication.