To provide a logical volume administration method capable of reducing a cost of using a storage, a logical volume is constructed by a steady area corresponding to a task of steadily allocating a disk area and a temporary area corresponding to a task of allocating no disk area until allocation of a disk area is requested. The disk area to be allocated to the temporary area is commonly used by a plurality of logical volumes in a time sharing manner. The disk areas are administered in a lump as a disk pool. The cost to each of customers sharing the temporary area is calculated by total use timeuse size and is charged.