System information

Table 6-3. Troubleshooting Fibre Channel LUN Display
Troubleshooting Task Description
Check cable connectivity. If you do not see a port, the problem could be cable connectivity. Check the cables first.
Ensure that cables are connected to the ports and a link light indicates that the connection
is good. If each end of the cable does not show a good link light, replace the cable.
Check zoning. Zoning limits access to specific storage devices, increases security, and decreases traffic
over the network. Some storage vendors allow only single-initiator zones. In that case, an
HBA can be in multiple zones to only one target. Other vendors allow multiple-initiator
zones. See your storage vendor’s documentation for zoning requirements. Use the SAN
switch software to configure and manage zoning.
Check access control
configuration.
n
The MASK_PATH plugin allows you to prevent your host form seeing a specific
storage array or specific LUNs on a storage array. If your host does not see the expected
LUNs on the array, path masking could have been set up incorrectly.
n
For booting from a SAN, ensure that each ESX host sees only required LUNs. Do not
allow any ESX host to see any boot LUN other than its own. Use storage system
software to make sure that the ESX host can see only the LUNs that it is supposed to
see.
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Ensure that the Disk.MaxLUN setting allows you to view the LUN you expect to see.
Check storage processor
setup.
If a disk array has more than one storage processor (SP), make sure that the SAN switch
has a connection to the SP that owns the LUNs you want to access. On some disk arrays,
only one SP is active and the other SP is passive until there is a failure. If you are connected
to the wrong SP (the one with the passive path), you might see the LUNs but get errors
when trying to access them.
Rescan your HBA. Perform a rescan each time you complete the following tasks:
n
Create new LUNs on a SAN.
n
Change the path masking configuration on an ESX/ESXi host storage system.
n
Reconnect a cable.
n
Make a change to a host in a cluster.
Storage Refresh and Rescan Operations
The refresh operation updates the datastore lists and storage information, such as the datastore capacity,
displayed in the vSphere Client. When you make changes in your ESX/ESXi host or SAN configuration, you
need to use the rescan operation.
You can rescan all adapters on your host. If the changes you make are isolated to a specific adapter, rescan
only this adapter. If your vSphere Client is connected to a vCenter Server system, you can rescan adapters on
all hosts managed by the vCenter Server system.
Perform a rescan each time you make one of the following changes.
n
Zone a new disk array on the SAN to an ESX/ESXi host.
n
Create new LUNs on a SAN.
n
Change the path masking on a host.
n
Reconnect a cable.
n
Make a change to a host in a cluster.
IMPORTANT Do not rescan when a path is unavailable. If one path fails, another takes over and your system
continues to be fully functional. If, however, you rescan at a time when a path is not available, the host removes
the path from its list of paths to the device. The path cannot be used by the host until the next time a rescan is
performed while the path is active.
Chapter 6 Managing ESX/ESXi Systems That Use SAN Storage
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