A virtual LUN (virtual logical unit number) is a representation
of a storage area that is not tied to any physical storage
allocation. Virtual LUNs are used in thin provisioning (also
known as virtual provisioning) for storage area network (SAN)
management. A virtual LUN is also sometimes called a thin LUN. A
logical unit number (LUN) is a unique identifier for a physical
storage allocation. A LUN could reference an entire RAID set, a
single hard disk or partition, or multiple disks or partitions.
Unlike a physical LUN, the virtual LUN does not map to a
specific device or allocation of storage space but a virtualized
space that can be created in excess of the actual physical space
available. In a SAN, hard disks are stored in physical racks.
The number of physical LUNs that can be created is limited by
the amount of space available and the RAID level. Virtual LUNs
remove that limitation. Because virtual LUNs are not tied to
physical devices or allocations, an administrator can create
large numbers of them tha