What is LUN, and how is it presented to a host?

• A. A LUN is a logical unit that provides file-level access to a host via NFS.
• B. A LUN is a logical unit representing a block storage device presented to a host via SAN protocols.
• C. A LUN is a network share for SMB.
• D. A LUN is a virtualization container for VMs.

Answer: (B)

A LUN is a logical unit of storage exposed by a storage array as a block device to a host over a SAN. It represents raw storage that the host can use at the block level, not a file or a network share. The array presents the LUN through SAN protocols (such as Fibre Channel or iSCSI), often masking it to specific initiators so only the intended host sees it. The host then detects the LUN as a SCSI disk (a block device) and can partition it, format a filesystem on top of it, or use it for raw block storage. This is distinct from file-level access (like NFS/SMB) or virtualized containers, which is why it’s presented as a block device rather than a network share.