Patent ID: 7130960

Claim:
A thin-provisioned storage subsystem for managing disk space comprising: a controller, the controller including a first port for providing a connection with at least one host device for I/O operations, a second port for providing a connection with an external storage subsystem, and a third port for providing a connection with an external console; and at least one storage device, the at least one storage device interconnected with the controller via a fourth port on the controller, wherein said storage subsystem includes the ability to perform at least one of transitioning logical devices (LDEVs) to a virtual device (VDEV) or adding logical devices from an external storage as free segments to a free segment pool, if a number of free segments in the free segment pool is below a desired minimum, the transitioning including identifying partially used or completely used LDEVs and transitioning these to the virtual device, and wherein each controller further comprises: a processor; and a memory, the memory including modules comprising: a virtual device manager, the virtual device manager creating and managing one or more thin-provisioning VDEV; a migrater, the migrater performing data migration from a LDEV to VDEV, from VDEV to LDEV, from VDEV to VDEV, and from LDEV to LDEV, a logical device manager, the logical device manager creating LDEVs to provide a logical storage from the at least one storage device to the at least host devices for the I/O operations; and a segment manager, the segment manager containing the free segment pool and managing the free segments in the free segment pool, wherein the memory stores a logical unit to logical device mapping and a disk to external logical unit mapping.