Patent ID: 8495254

Claim:
A computer system comprising: a server being configured to manage a first virtual machine to which a first part of a server resource included in the server is allocated and a second virtual machine to which a second part of the server resource is allocated; a storage apparatus including a storage controller, a cache memory and a plurality of storage devices; and a management terminal coupled to the storage apparatus; wherein the storage apparatus is configured to create a first virtual storage apparatus to which a first storage area on the plurality of storage devices and a first capacity of the cache memory is allocated and a second virtual storage apparatus to which a second storage area on the plurality of storage devices and a second capacity of the cache memory is allocated, wherein the first capacity and the second capacity of the cache memory is instructed by the management terminal, wherein the first virtual machine corresponds to the first virtual storage apparatus, and the second virtual machine corresponds to the second virtual storage apparatus, wherein the first virtual storage apparatus has a first virtual storage identifier and the second virtual storage apparatus has a second virtual storage identifier, wherein the first storage area has a first storage area identifier and the second storage area has a second storage area identifier, wherein a first I/O command, which is issued by the first virtual machine to the first virtual storage apparatus, includes the first virtual storage identifier and a first disk I/O command, and wherein if the storage apparatus receives the first I/O command, the I/O command is transferred to the first virtual storage apparatus by referring the first virtual storage identifier included in the first I/O command to execute the first disk I/O command by the first virtual storage apparatus.