Patent ID: 8095752

Claim:
A storage access device, which issues an I/O request (input/output request) to a logical unit provided by one or more storage systems, comprising: logical volumes corresponding to the logical units respectively; a volume manager for managing association information, which shows that a plurality of the logical volumes corresponding to a plurality of the logical units belonging to the same copy-set are associated; a virtual device, to which the associated logical volumes shown by the association information are allocated respectively, and which is provided to an application; and wherein the volume manager further manages, for each the logical volume, role information showing whether a logical volume corresponds to a primary volume or a secondary volume, and update time information showing the latest point in time at which the storage access device issued a write request to the logical volume, the storage access device further comprising: an I/O request issuer, which, when a read indication specifying the virtual device is received from the application, references the association information, role information, and update time information managed by the volume manager, selects from among the logical volumes allocated to the virtual device the logical volume corresponding to the primary volume and the logical volume holding the same update time information as the logical volume corresponding to the primary volume, and issues a read request to at least one of the selected logical volumes, and wherein the primary volume is the logical volume corresponding to a primary logical unit; the secondary volume is the logical volume corresponding to a secondary logical unit; the primary logical unit is the logical unit, which constitutes a copy-source, but does not constitute a copy-destination in the copy-set; and the secondary logical unit is the logical unit, which constitutes the copy-destination in the copy-set.