It is necessary to install a program called an agent in order to keep track of how much a file system on a computer uses a disk. On this account, loads might be applied to a server due to installation work or the agent program to increase primary costs. In addition, software inside a storage device determines and records a target block for data input/output and keeps track of capacity utilization, which might degrade the input/output performance of the storage device. A computer system is provided in which configuration information and operating information are acquired from a storage device, when data input/output is made from a computer to a logical unit, it is determined that the computer uses the logical unit to which input/output is made, and capacity used by the computer is computed.