Some LARGE LUN Numbers Are Not Available to the Computer

Article translations Article translations
Article ID: 245637 - View products that this article applies to.
This article was previously published under Q245637
This article has been archived. It is offered "as is" and will no longer be updated.
Expand all | Collapse all


When you configure a computer to use LARGE LUN Support, such as on a Fibre Channel controller, some of the LUNs assigned to disks or other devices are not visible to other system drivers or the computer.

Only 231 of the 256 possible LUNs are visible. The LUNs that are not visible are in the following ranges:
64 to 71
128 to 135
192 to 199


A supported fix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Apply it only to computers that are experiencing this specific problem.

To resolve this problem, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, visit the following Microsoft Web site:;EN-US;CNTACTMS
NOTE: In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

The English-language version of this fix should have the following file attributes or later:
   Date        Time     Size     File name     Platform
   10/25/1999  01:57p   35,504   Scsiport.sys  i386
   10/25/1999  01:56p   56,400   Scsiport.sys  alpha
For more information on LargeLun support in Windows, click the following article number to view the article in the Microsoft Knowledge Base:
310072 Adding support for more than eight LUNs in Windows Server 2003 and in Windows 2000


Microsoft has confirmed that this is a problem in Windows NT 4.0.


Article ID: 245637 - Last Review: February 28, 2014 - Revision: 2.4
  • Microsoft Windows NT 4.0 Service Pack 5
  • Microsoft Windows NT 4.0 Service Pack 6
  • Microsoft Windows NT Workstation 4.0
  • Microsoft Windows NT Workstation 4.0 Developer Edition
kbnosurvey kbarchive kbhotfixserver kbqfe kbbug kbfix KB245637

Give Feedback


Contact us for more help

Contact us for more help
Connect with Answer Desk for expert help.
Get more support from