An ESXi host is limited to accessing 256 SCSI storage devices, but the range of LUN IDs can be from 0 to 1023. ESXi ignores LUN IDs that are 1024 or greater. This limit is controlled by Disk.MaxLUN, which has a default value of 1024.

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The value of Disk.MaxLUN also determines how many LUNs the SCSI scan code attempts to discover by using individual INQUIRY commands if the SCSI target does not support direct discovery by using REPORT_LUNS.

You can modify the Disk.MaxLUN parameter depending on your needs. For example, if your environment has a smaller number of storage devices with LUN IDs from 0 to 100, you can set the value to 101 to improve device discovery speed on targets that do not support REPORT_LUNS. Lowering the value can shorten the rescan time and boot time. However, the time to rescan storage devices might depend on other factors, including the type of storage system and the load on the storage system.

In other cases, you might need to increase the value if your environment uses LUN IDs that are greater than 1023.


  1. Click Manage in the VMware Host Client inventory and click Advanced Settings.
  2. Scroll down to Disk.MaxLUN.
  3. Right-click Disk.MaxLUN, and click Edit option.
  4. Enter a new value and click Save.

    The SCSI scan code does not scan the LUNs with IDs greater than or equal to the value you enter.

    For example, to discover LUN IDs from 0 to 100, set Disk.MaxLUN to 101.