The storage system is capable of creating one or more virtual storage subsystems to which virtual resources having logically divided a processing capacity of the physical resources are allocated, and upon creating a virtual volume for receiving I/O requests from the host within the virtual storage subsystem, the virtual storage subsystem allocates the virtual resource to the virtual volume, and when an I/O request to the virtual volume is received from the host, performs processing related to the I/O request using the virtual resource having been allocated. According further to the storage system, after allocating the virtual resource to the virtual volume, the storage system raises a utilization rate of the virtual resource allocated to the virtual volume in a stepwise manner.