A SAN manager acquires configuration information from devices constituting a SAN and produces a corresponding relationship between a host computer and a virtual volume (virtual volume mapping) and a corresponding relationship between the host computer and a real volume (real volume mapping). Based on those pieces of mapping information, the SAN manager outputs a corresponding relationship between virtual and real volumes. Meanwhile, the failure notification messages received from the in-SAN devices are construed to detect and output an influence of the failure upon the access to a real or virtual volume. Furthermore, when receiving a plurality of failure notifications from the devices connected to the SAN, the plurality of failure notifications are outputted with an association based on the corresponding relationship between real and virtual volumes.