Patent ID: 7136983

Claim:
A method of increasing an amount of memory 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 the asynchronous mode; providing a first memory in a queuing area of the first storage subsystem and a second memory 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 memory and storing the data in the remote secondary volume; and monitoring an unused area of the queuing area of the first storage system and increasing an amount of the first memory therein when the unused area becomes less than a predetermined amount.