Patent ID: 7139885

Claim:
A method for making a remote copy between a first storage subsystem and a second storage subsystem which are connected to each other via a path, the first storage system connected to a first host, the method comprising: providing a first logical volume to the first storage subsystem and a second logical volume to the second storage subsystem; copying the contents of the first logical volume to the second logical volume, the first logical volume and the second logical volume being in sync state; making a third logical volume in the first storage subsystem and copying first data from the first logical volume to the third logical volume, the first logical volume and the third logical volume being in sync state; making a fourth logical volume in the second storage subsystem and copying second data from the second logical volume to the fourth logical volume, the second logical volume and the fourth logical volume being in sync state, wherein the copying of the second data is performed after the copying the contents of the first logical volume to the second logical volume; after the copying of the first data from the first logical volume to the third logical volume, breaking the sync state between the first logical volume and the third logical volume; after copying of the second data from the second logical volume to the fourth logical volume breaking the sync state between the second logical volume and the fourth logical volume based on a command; after the copying of the first data from the first logical volume to the third logical volume and after copying of the second data from the second logical volume to the fourth logical volume, establishing a synchronization link between the fourth logical volume and the third logical volume; coupling a first auxiliary host to the third logical volume; and enabling the first auxiliary host to perform operations on the third logical volume while the first host continues operations on the first logical volume and while the first logical volume and second logical volume continue in sync state.