Patent ID: 7509455

Claim:
A system comprising: a computer; a virtualization apparatus having at least one virtual volume, the virtualization apparatus coupled to the computer; and a storage system having at least one real volume associated with the virtual volume, the storage system coupled to the virtualization apparatus, wherein the virtualization apparatus provides data stored in the real volume as data in the virtual volume to the computer, wherein the computer sends write data for the virtual volume to the virtualization apparatus, wherein the virtualization apparatus receives the write data, encrypts the write data, and sends encrypted data for the real volume to the storage system, and wherein the storage system receives the encrypted data and stores the encrypted data into the real volume, wherein the virtualization apparatus has a cache, wherein the virtualization apparatus receives the write data for the virtual volume, stores the write data in the cache, sends a reply to the computer, encrypts and sends the write from the cache to the real volume in the storage system, wherein the virtualization apparatus further has information indicating whether the cache is used for each of the plural virtual volumes, when the virtual apparatus receives an access request for a virtual logical volume from the computer, wherein the virtualization apparatus is configured to determine whether the cache is used for the virtual volume based on the information, and wherein if the cache is used for the virtual logical volume and the access request is a write request, the first storage system is configured to store the write data in the cache, to encrypt the write data in the cache and to send the write data to the storage system at asynchronous timing of the write request.