A method for storage management is provided which displays the materials on which it is determined which of the thin provisioning volume or the logical unit (LU) is to be used for storage promotion. The method is executed in a computer system having one or more host computers, one or more storage subsystems, and a management computer. The storage subsystem includes a physical disk and a disk controller. The disk controller provides the host computer with the thin provisioning volume. The management computer obtains the allocated capacity from the disk controller and the host-recognized capacity from the host computer. By subtracting the obtained allocated capacity from the host-recognized capacity, the management computer calculates an improved capacity. By dividing the calculated improved capacity by the obtained host-recognized capacity, the management computer calculates an improvement ratio and displays the calculated improvement ratio.