Patent ID: 7555622

Claim:
A method of increasing an amount of storage capacity in a queuing area on demand in a storage system implementing a remote mirroring function, said storage system including first and second storage subsystems which are connected to each other via a path and the first storage subsystem being connected to a host, the method comprising the steps of: providing a primary volume to the first storage subsystem and a remote secondary volume to the second storage subsystem, the remote secondary volume being a copied volume of the primary volume, the primary volume and the remote secondary volume being operated in an asynchronous mode; providing a first storage in a queuing area of the first storage subsystem and a second storage in a queuing area of the second storage subsystem for temporarily storing data transferred from the first storage subsystem to the second storage subsystem in response to a write input/output (I/O) issued by the host to write data in the primary volume; retrieving data temporarily stored in the second storage and storing the data in the remote secondary volume; and monitoring an unused area of the queuing area in the first storage system so as to increase an amount of the first storage when the unused area of the queuing area of the first storage system becomes less than a predetermined amount.