The range of scanned LUN IDs for an ESXi host can be from 0 to 16,383. ESXi ignores LUN IDs greater than 16,383. The configurable Disk.MaxLUN parameter controls the range of scanned LUN ID range. The parameter has a default value of 1024.

The Disk.MaxLUN parameter also determines how many LUNs the SCSI scan code attempts to discover using individual INQUIRY commands if the SCSI target does not support direct discovery 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 1 through 100, set the value to 101. As a result, you can 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 also depend on other factors, including the type of the 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.

Procedure

  1. In the vSphere Client, navigate to the ESXi host.
  2. Click the Configure tab.
  3. Under System, click Advanced System Settings.
  4. In the Advanced System Settings table, select Disk.MaxLUN and click the Edit icon.
  5. Change the existing value to the value of your choice, and click OK.
    The value you enter specifies the LUN ID that is after the last one you want to discover.
    For example, to discover LUN IDs from 1 through 100, set Disk.MaxLUN to 101.