Patent ID: 8458421

Claim:
A storage system comprising: a plurality of storage devices including a plurality of types of storage devices, each of the type of storage devices having a performance that is different from each of the other types of storage devices, and providing a plurality of pool areas; and a controller, wherein the controller is configured to: provide a primary logical volume and a secondary logical volume to be paired with the primary logical volume; allocate a plurality of pool areas, each of the plurality of pool areas being provided by one of the plurality of types of storage devices, to a plurality of first logical areas in the primary logical volume to store write data; change the allocation of each of the plurality of first logical areas to another pool area provided by another type of the storage devices based on an access status of each of the plurality of first logical areas; when a command to pair the primary logical volume with the secondary logical volume is received, copy data from the plurality of first logical areas in the primary logical volume to the plurality of corresponding second logical areas in the secondary logical volume, and store the copied data in a plurality of pool areas provided by the same type of storage device with the pool area storing the copied data in the first logical volume and allocated to the plurality of corresponding second logical areas in the secondary logical volume; and when a state transition command relating to the pair is received, migrate data stored in the pool area, allocated to at least one of the first logical area or second logical area, to the another pool area provided by the another type of storage devices and change the allocation of the at least one of the second logical area.