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Troubleshooting LUN connectivity issues on ESXi/ESX hosts (1003955)

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  • Targets on the storage array are visible but one or more LUNs are not visible
  • LUN not visible
  • LUN cannot connect
  • LUN is missing
  • LUN not presented


This article assists you in troubleshooting a scenario where LUNs are missing.


Validate that each troubleshooting step below is true for your environment. Each step provides instructions or a link to a document, in order to eliminate possible causes and take corrective action as necessary. The steps are ordered in the most appropriate sequence to isolate the issue and identify the proper resolution. Do not skip a step.

These steps assist you in identifying a LUN connectivity issue:

  1. Verify that the LUN is presented to the ESXi/ESX host. You may need to contact your array vendor for assistance.

    1. Verify that the LUN is in the same storage group as all the ESXi/ESX hosts (if applicable to the array).
    2. Verify that the LUN is configured correctly for use with the ESXi/ESX host.

      Note: Consult the appropriate SAN configuration guide for your array (listed in the Additional Information section).

    3. Verify that the LUN is not set to read-only on the array.
    4. Ensure that the HOST ID on the array for the LUN (on ESX it shows up under LUN ID) is less than 255 for the LUN. The maximum LUN ID is 255. Any LUN that has a HOST ID greater than 255 may not show as available under Storage Adapters, though on the array they may reside in the same storage group as the other LUNs that have host IDs less than 255. This limitation exists in all versions of ESXi/ESX from ESX 2.x to ESXi 5.x due to the fact that SCSI lun ID field in hexadecimal range 00 -FF (256). This information can be found in the maximums guide for the particular version of ESXi/ESX having the issue.

  2. Verify that the ESX /ESXi host can see the LUNs. For more information, see Obtaining LUN pathing information for ESX or ESXi hosts (1003973).

    Note: If LUNs are not visible on the ESXi/ESX host, see:

  3. Verify that a rescan restores visibility to the LUN(s). For more information, see Performing a rescan of the storage on an ESXi/ESX host (1003988) and Interpreting SCSI sense codes in VMware ESX / ESXi (multiple versions) (289902).

  4. Check the storage for latency. For more information, see Using esxtop to identify storage performance issues (1008205).

  5. Verify that there are not excessive SCSI reservation conflicts. For more information, see:

  6. For issues related to a VMFS datastore, see:

Note: If your problem still exists after trying the steps in this article:

Additional Information

For ESXi 5.0, see:
For ESXi/ESX 4.1, see:
For ESXi/ESX 4.0, see: For ESX Server 3.5 and 3i (Embedded and Installable), see:
For ESXi/ESX 3.x, see:

For translated versions of this article, see:



See Also

Update History

06/13/2012 - Added links to additional 5.x resources. 06/07/2012 - Updated for 5.x

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