The computer system executes a storage program that operates on an OS to provide a logical volume to a host. The computer system includes volume management information including information on a storage function to be applied to the logical volume provided by the storage program. Upon receiving an I/O request for the logical volume from the host, the OS determines whether it is necessary for the storage program to perform an I/O process on the basis of the information on the storage function to be applied to the logical volume by referring to the volume management information. When it is determined that the I/O process is necessary, the OS communicates with the storage program and the storage program executes the I/O process. When it is determined that it is not necessary for the storage program to perform the I/O process, the OS outputs an I/O response to the host.