4.1 Virtualization definition4.2 Benefits of virtualization4.3 Abstraction layers for drive virtualization4.3.1 Array sites4.3.2 Arrays4.3.3 Ranks4.4 Extent pools4.4.1 Dynamic extent pool merge4.4.2 Logical volumes4.4.3 Allocation, deletion, and modification of LUNs and CKD volumes4.4.4 Volume allocation and metadata4.4.5 Logical subsystems4.4.6 Volume access4.4.7 Virtualization hierarchy summary