In a SAN (Storage Area Network), if all the hosts are allowed to access all the drives in the SAN, it may lead to many issues like device contention and mainly data corruption. In addition some Operating Systems (eg. Windows ) writes header information to disks which will lead to data loss (We will discuss it later in this article). To avoid this zoning and LUN masking is used. By doing Zoning and LUN masking storage units are isolated or made invisible to some or all of the hosts in the SAN. Lets look into zoning and LUN masking in detail.