Patent ID: 8656136

Claim:
A storage system comprising: a storage device; and a storage controller which is coupled to the storage device and a server computer providing a virtual computer, and provides a storage level virtual volume, wherein the storage controller is configured to manage a storage area of the storage device as a plurality of low-level storage areas by dividing the storage area into first management units, manage a block address space of the storage level virtual volume as a plurality of low-level address areas by dividing the block address space into second management units of a size related to the first management units, and store low-level area conversion information indicating the low-level storage areas which are allocated to the low-level address areas, wherein the server computer is configured to provide a server level virtual volume to the virtual computer, manage the storage level virtual volume as a plurality of high-level storage areas by dividing the storage level virtual volume into third management units, manage a block address space of the server level virtual volume as a plurality of high-level address areas by dividing the block address space into fourth management units related to the third management units, and store high-level area conversion information indicating the high-level storage areas which are allocated to the high-level address areas, wherein the storage system is configured to receive a clear request specifying a block address range, identify a prescribed low-level address area included in the specified block address range and release a prescribed low-level address area allocated to the prescribed low-level address area, wherein the clear request is sent by the server computer, and the block address range specified by the clear request is a block address range of a prescribed high-level storage area allocated to the high-level address area included in the server level virtual volume provided to the virtual computer specified by a virtual machine request received by the server computer.