Storage Manager for SANs helps you create and manage logical unit numbers (LUNs) on Fibre Channel and iSCSI disk drive subsystems that support Virtual Disk Service (VDS) in your storage area network (SAN).
A LUN is a logical reference to a portion of a storage subsystem. A LUN can comprise a disk, a section of a disk, a whole disk array, or a section of a disk array in the subsystem. Using LUNs simplifies the management of storage resources in your SAN because they serve as logical identifiers through which you can assign access and control privileges.