KnowledgeBase Archive

An Archive of Early Microsoft KnowledgeBase Articles

View on GitHub

Q243869: Using More Than Eight LUNs Per SCSI ID

Article: Q243869
Product(s): Microsoft Windows NT
Version(s): winnt:4.0 SP4,4.0 SP5,4.0 SP6,4.0 SP6a
Operating System(s): 
Keyword(s): kbenv kbhw kbHardware
Last Modified: 06-AUG-2002

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Windows NT Server versions 4.0 SP4, 4.0 SP5, 4.0 SP6, 4.0 SP6a 
- Microsoft Windows NT Workstation versions 4.0 SP4, 4.0 SP5, 4.0 SP6, 4.0 SP6a 
-------------------------------------------------------------------------------

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:

  Q256986 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 255 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.

Additional query words:

======================================================================
Keywords          : kbenv kbhw kbHardware 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400search kbWinNT400search kbWinNTW400sp5 kbWinNTW400sp4 kbWinNTSsearch kbWinNTS400sp6 kbWinNTS400sp5 kbWinNTS400sp4 kbWinNTS400search kbWinNTW400sp6 kbWinNTW400SP6a
Version           : winnt:4.0 SP4,4.0 SP5,4.0 SP6,4.0 SP6a
Issue type        : kbinfo

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.