When we use a Disk Subsystem, the HBA can be restricted to only discovering resources that it is allowed to use.
The RAID or Subsystem Configuration Utility supports LUN Masking. This allows us to configure which hosts are permitted to see which Logical Units.
The mask is created by assigning the HBAs unique worldwide name, typically the World Wide Port Name, to each Logical Unit. This means that when the host scans for its resources, the Subsystem will only advertise back the LUNs that that particular host is allowed to use.
As the HBA only discovers the permitted resources, we can simplify operations by enabling Automap on the HBA so each Logical Unit is automatically made visible to the hosts volume manager.