Scsiport.sys Does Not Enumerate External Storage Correctly

ID: Q232896

The information in this article applies to:
IMPORTANT: This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore it if a problem occurs. For information about how to do this, view the "Restoring the Registry" Help topic in Regedit.exe or the "Restoring a Registry Key" Help topic in Regedt32.exe.

SYMPTOMS

Computers running Windows NT Server 4.0 Service Pack 4 (SP4) with the Qlogic 2100F SCSI adapter may experience unexpected behavior from the driver. When you start Disk Administrator and then view each adapter, more drives are displayed than are actually configured on each adapter.


CAUSE

This problem occurs because features were added to SP4 for configurations where large numbers of devices were being used. The Qlogic driver also has this ability built into it.


RESOLUTION

WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys and Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it. If you are running Windows NT, you should also update your Emergency Repair Disk (ERD).

With Windows NT 4.0 Service Pack 4, a new registry entry was added to support more than eight logical unit numbers (LUNs). With this registry setting, up to 255 LUNs are supported. To enable this feature, the following registry value must be added to the system:

  1. Start Registry Editor (Regedt32.exe).


  2. Locate the following key in the registry: 
    
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Driver_Service_Key
   \Parameters\Device[Number]
    NOTE: The above registry key is one path; it has been wrapped for readability.


  3. On the Edit menu, click Add Value, and then add the following registry value: 


    4. 
   Value Name: LargeLuns
   Data Type:  REG_DWORD
   Value:      0x1

Where Driver_Service_Key is the SCSI driver name and [Number] is the SCSI adapter number (0 for the first adapter, 1 for the second adapter, and so forth) controlled by this specific driver.

If [Number] is not specified, this registry value will apply to all the adapters described by the Driver_Service_Key. To disable Large LUN support, either delete the LargeLun registry value or change the value to 0 (zero).

When the value is set to 0, Large LUN support by the QLogic driver is disabled and Scsiport.sys enumerates the drives correctly.
  4. Quit Registry Editor.



STATUS

Microsoft has confirmed this to be a problem in Windows NT Server 4.0 Service Pack 4.


MORE INFORMATION

The unexpected behavior occurs when both the Windows NT LargeLuns feature is enabled along with the Qlogic LargeLuns feature.

Additional query words: 


Keywords          : 
Version           : winnt:4.0 SP4
Platform          : winnt 
Issue type        : kbbug kbprb

Last Reviewed: June 28, 1999