Patent ID: 7716419

Claim:
A computer system comprising: a host computer that requests the input and output of data in and from an actual storage volume; and a storage system including a plurality of storage subsystems each of which has actual I/O ports and is configured with at least one corresponding virtual storage volume, wherein each virtual storage volume of each of said storage subsystems is mapped into a common external volume but presented to said host computer as an internal storage volume of the corresponding storage subsystem, wherein said common external volume is physically located outside of said host computer and said storage subsystems, wherein each of said storage subsystems includes at least one actual storage volume physically located therein, wherein each actual storage volume of each of said storage subsystems and said common external volume are each assigned with a different globally unique identifier (GUID), wherein each virtual storage volume of each of said storage subsystems shares the GUID assigned to said common external volume, and wherein said host computer identifies a plurality of logical paths to be respectively connected through each of said virtual storage volumes to said common external volume by scanning for the shared GUID, and sets one of the logical paths to request the input and output of data in and from said common external volume.