In a SAN, if Host A can access LUNs and Host B cannot access LUN 11, what is the most likely cause?

In a SAN, if Host A can access LUNs and Host B cannot access LUN 11, what is the most likely cause?

• A. Faulty fiber HBA
• B. Incorrect HBA WWPN
• C. Incorrect HBA software version
• D. Defective HBA

Answer: (B)

In a SAN, what a host can see is controlled by LUN masking and the fabric’s zoning, both keyed to the host’s HBA WWPN (World Wide Port Name). If another host can access multiple LUNs but a specific LUN isn’t visible to the second host, the most likely issue is that the HBA WWPN on that host is not correctly registered or allowed for that LUN. When the array’s masking (and the fabric zoning) doesn’t include the host’s WWPN for that LUN, the storage system simply won’t present that LUN to the host, even though other LUNs are accessible to other hosts. This is more selective than a hardware fault or software version mismatch. A truly faulty HBA would typically disrupt access to all LUNs, not just one. The same goes for a software version issue—it would tend to affect broader functionality or compatibility rather than isolating a single LUN. Defective hardware would usually cause broader connectivity problems as well. By contrast, an incorrect WWPN means the host is effectively not recognized for that specific LUN in the array’s access rules, which neatly explains why LUN 11 is unavailable to that host.

In a SAN, what a host can see is controlled by LUN masking and the fabric’s zoning, both keyed to the host’s HBA WWPN (World Wide Port Name). If another host can access multiple LUNs but a specific LUN isn’t visible to the second host, the most likely issue is that the HBA WWPN on that host is not correctly registered or allowed for that LUN. When the array’s masking (and the fabric zoning) doesn’t include the host’s WWPN for that LUN, the storage system simply won’t present that LUN to the host, even though other LUNs are accessible to other hosts.

This is more selective than a hardware fault or software version mismatch. A truly faulty HBA would typically disrupt access to all LUNs, not just one. The same goes for a software version issue—it would tend to affect broader functionality or compatibility rather than isolating a single LUN. Defective hardware would usually cause broader connectivity problems as well. By contrast, an incorrect WWPN means the host is effectively not recognized for that specific LUN in the array’s access rules, which neatly explains why LUN 11 is unavailable to that host.