A disaster recovery technology capable of achieving the high-speed FO and correctly reading the logs even if the unit of logs written in the main site is large is provided. In the disaster recovery system comprising a main site and a sub-site, when the writing in units of a log block consisting of a plurality of log records is performed in the main site and the logs are applied in the sub-site, the log blocks are read from the sub-storage to verify the consistency, and it is determined whether the reading process conflicts with the writing process through the remote copy operation when reading the logs. Then, only the log blocks in which the reading process does not conflict with the writing process as a result of the determination are applied to the database. Thereby, the logs are applied in the sub-site independently to recover the database.