While an ESXi host is limited to accessing 256 SCSI storage devices, the range of LUN IDs can be from 0 to 1023. ESXi ignores LUN IDs 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 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 0 through 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.
- In the vSphere Client inventory panel, select the host, click the Configuration tab, and click Advanced Settings under Software.
- Select Disk.
- Scroll down to Disk.MaxLUN.
- Change the existing value to the value of your choice, and click OK.
The value you enter specifies the LUN ID after the last one you want to discover.
For example, to discover LUN IDs from 0 through 100, set Disk.MaxLUN to 101.