Using More Than Eight LUNs Per SCSI ID (243869)


The information in this article applies to:

  • Microsoft Windows NT Server 4.0 SP4
  • Microsoft Windows NT Server 4.0 SP5
  • Microsoft Windows NT Server 4.0 SP6
  • Microsoft Windows NT Server 4.0 SP6a
  • Microsoft Windows NT Workstation 4.0 SP4
  • Microsoft Windows NT Workstation 4.0 SP5
  • Microsoft Windows NT Workstation 4.0 SP6
  • Microsoft Windows NT Workstation 4.0 SP6a
This article was previously published under Q243869
IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows Registry

SUMMARY

Windows NT 4.0 with Service Pack 4 (SP4) or later supports a new registry value that allows more than 8 logical unit numbers (LUNs). With this new registry setting, up to 254 LUNs are supported.

MORE INFORMATION

WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

To enable this feature, add the following registry value

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Driver_Name\Parameters\Device#\LargeLuns: REG_DWORD: 0x1

where Driver_Name is the SCSI driver name and Device# is the SCSI adapter number (0 for the first adapter, 1 for the second adapter, and so on) controlled by this specific driver.

NOTE: You can omit the Device# key, but if it is present, it represents the adapter instance number. If Device# is not present, the LargeLuns registry value applies to all the adapters described by Driver_Name. To disable large LUN support, either delete the LargeLuns registry value or change the data value to 0 (zero).

Note that this feature works only if the SCSI controller and devices support the REPORT_LUNS command. If not, you see only LUNS 0 through 7, no matter what you set the LargeLuns value to. If the SCSI controller for the computer does not support the REPORT_LUNS command, Windows NT uses only LUNs 0 through 7.

Contact your OEM SCSI controller manufacturer to determine how many LUNs your SCSI controller supports.
Modification Type:MinorLast Reviewed:4/26/2004
Keywords:kbenv kbHardware kbinfo KB243869
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