Troubleshooting LUN connectivity issues on ESXi hosts
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Troubleshooting LUN connectivity issues on ESXi hosts

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Article ID: 323129

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Updated On: 04-11-2025

Products

VMware vSphere ESXi

Issue/Introduction

This article provides troubleshooting steps when LUNs are missing:

  • 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

Environment

  • VMware vSphere ESXi 7.x
  • VMware vSphere ESXi 8.x

Resolution

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.
  1. Verify that the LUN is presented to the ESXi 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 hosts (if applicable to the array).
    2. Verify that the LUN is configured correctly for use with the ESXi 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. If you are presenting LUN IDs that are higher than 255, please ensure Disk.MaxLUN setting on the ESXi host is set higher than the range you are using. Please see:Changing the Disk.MaxLUN parameter on ESXi Hosts Further...
      1. If you are presenting (in total) more than 255 LUNs from an array, please make sure that your HBA driver supports it, for example Cisco UCS manager has a "Max LUNs Per Target" field that is defaulted to 256,but is recommended to be 1024 for ESXi hosts.
  2. Verify that the ESXi  host can see the LUNs. For more information, see Obtaining LUN pathing information for ESXi hosts.

    Note: If LUNs are not visible on the ESXi 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 host and Interpreting SCSI sense codes in VMware ESXi.
     
  4. Check the storage for latency. For more information, see Using esxtop to identify storage performance issues for ESXi (multiple versions).
     
  5. Verify that there are not excessive SCSI reservation conflicts. For more information, see: Resolving SCSI reservation conflicts.
Note: If your problem still exists after trying the steps in this article:

Additional Information

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