DOCUMENT:Q243869 06-AUG-2002 [winnt] TITLE :Using More Than Eight LUNs Per SCSI ID PRODUCT :Microsoft Windows NT PROD/VER:winnt:4.0 SP4,4.0 SP5,4.0 SP6,4.0 SP6a OPER/SYS: KEYWORDS:kbenv kbhw kbHardware ====================================================================== ------------------------------------------------------------------------------- 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\\Parameters\\LargeLuns: REG_DWORD: 0x1 where is the SCSI driver name and 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 key, but if it is present, it represents the adapter instance number. If is not present, the LargeLuns registry value applies to all the adapters described by . 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. Copyright Microsoft Corporation 2002.