Home » VMware » VCP550D » What is the most likely cause?
A new LUN from an existing storage array is presented to a vSphere cluster. A vSphere administrator determines that the LUN is visible on all but one ESXi host in the cluster. The affected host is able to see existing LUNs presented from the same storage array.
What is the most likely cause?
A. LUN Masking is improperly configured on the storage array.
B. The SAN fabric is improperly zoned.
C. The ESXi host has NOT been rebooted.
D. The HBA in the host is incompatible with ESXi.
Correct Answer: A
Explanation/Reference:
Explanation:
The most likely cause of the problem is that incorrectly configured LUN masking is preventing access to the LUN for the ESXi host.
To transfer traffic from host servers to shared storage, the SAN uses the Fibre Channel (FC) protocol that packages SCSI commands into Fibre Channel frames.
To restrict server access to storage arrays not allocated to that server, the SAN uses zoning. Typically, zones are created for each group of servers that access a shared group of storage devices and LUNs. Zones define which HBAs can connect to which storage processors. Devices outside a zone are not visible to the devices inside the zone.
Zoning is similar to LUN masking, which is commonly used for permission management. LUN masking is a process that makes a LUN available to some hosts and unavailable to other hosts.
Incorrect Answers:
B: If the SAN fabric was improperly zoned, the affected host would not be able to see existing LUNs presented from the same storage array. Therefore, this answer is incorrect.
C: It is not necessary to reboot the host; we can just perform a storage rescan. However, we know that the host is able to see the SAN. Therefore, this answer is incorrect.
D: If the HBA in the host is incompatible with ESXi, the host would not be able to see existing LUNs presented from the same storage array. Therefore, this answer is incorrect.
References:
http://pubs.vmware.com/vsphere-55/index.jsp#com.vmware.vsphere.storage.doc/GUID-39A4551F-4B03-43A6-BEDF-FAB1528C070D.html
