Patent ID: 7197609

Claim:
A virtualization system coupled to a first and second storage system which stores data written by a host computer, the first and second storage system presenting at least one storage volume as a storage resource to the virtualization system, the virtualization system presenting at least one virtual volume as a storage resource to the host computer, the virtualization system comprising: a first interface to be coupled to the host computer sending an I/O request; a second interface to be coupled to the first storage system storing data written by the host computer; a third interface to be coupled to the second storage system storing data written by the host computer; and a processor being configured to manage a first storage volume configured with at least one of storage devices in the first storage system as a first virtual volume and to manage a second storage volume configured with at least one of storage devices in the second storage system as a second virtual volume; wherein, when the virtualization system receives a request to change an attribute of the first virtual volume to write protect state, the virtualization system restricts the host computer from write access to the first storage volume via the first and second interface and further issues a request to write-protect the first storage volume to the first storage system, wherein, when the virtualization system receives a request to change an attribute of the second virtual volume to write protect state, the virtualization system restricts the host computer from write access to the second storage volume via the first and third interface and further issues a request to write-protect the second storage volume to the second storage system.