Storage system and storage control method

A storage system comprising:

• a storage device group that includes one or more storage devices, wherein each of the one or more storage device includes;
• a storage medium that includes a plurality of physical areas, and
• a medium controller communicatively coupled to the storage medium, wherein the medium controller provides a logical space configured with a plurality of logical areas and allocates a respective physical area from the plurality of physical areas to a respective logical area from the plurality of logical areas;
• a plurality of real areas that each correspond to one or more logical areas respectively provided by the one or more storage devices, wherein user data stored in a first real area from the plurality of real areas are respectively stored in one or more physical areas respectively allocated to one or more logical areas corresponding to the first real area,
• a storage controller that manage the plurality of real areas, wherein the storage controller;
• manage a first virtual volume that includes a plurality of first virtual areas and to which the first real area is allocated,
• manages a second virtual volume that includes a plurality of second virtual areas as a clone of the first virtual volume,
• allocates a second real area to a particular second virtual area before a write occurs in the particular second virtual area corresponding to a particular first virtual area to which the first real area is allocated,
• receive a write request that specifies the second virtual volume from a host computer,
• manages an access load of each second virtual area,
• determines whether there is a low-access load area that is the particular second virtual area having the access load being a predetermined load or less, and
• releases the second real area from the low-access load area, and allocate the first real area to the low-access load area when there is the low-access load area, and the second real area is allocated to the low-access load area;
• and
• wherein the medium controller of each of the storage devices allocates a particular physical area allocated to the logical area corresponding to the first real area to a particular logical area corresponding to the second real area.