Patent ID: 7139851

Claim:
A method for recovering and maintaining data consistency between volumes of first and second storage systems which are connected to each other via a path, the first storage system being connected to a host, the method comprising the steps of: providing a primary volume to the first storage system and a remote secondary volume to the second storage system, the remote secondary volume being a copied volume of the primary volume, the primary volume and the remote secondary volume being in synchronous mode; providing a local secondary volume in the first storage system, the local secondary volume being a logical volume separate from the primary volume, the local secondary volume having stored therein journal logs of write input/output (I/O) commands issued by the host to the primary volume to store write data in the primary volume and old data including write data of the write I/O commands; and conducting recovery of data on the primary volume from the local secondary volume when necessary by performing recovery of data of the primary volume based on the old data and the journal logs while maintaining the primary volume and the remote secondary volume in the synchronous mode.