With storage area networks (SANs), a logical unit number (LUN) is a logical reference to a portion of the storage subsystem. A LUN is fairly analogous to a volume in that you can use it to represent all or part of a disk as well as all or part of an array of disks. As with volumes, you can assign access and control privileges on a per-LUN basis.
Like volumes, LUNs come in several varieties:
Simple. A simple LUN uses only one physical drive or one portion of a physical drive.
Spanned. A spanned LUN is a simple LUN that spans multiple physical drives.
Striped. A striped LUN writes data across multiple physical drives. Striped LUNs don’t offer fault tolerance and can’t be extended or mirrored. If one of the disks containing a striped ...