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Cache Manager May Cause Data Corruption on SMB Servers on FAT

This article was previously published under Q179433
This article has been archived. It is offered "as is" and will no longer be updated.
You may encounter corrupted files if Windows NT is installed on a FATpartition or shared CDFS volume that has a file system filter driverrunning on that volume.
This problem is caused by Memory Descriptor List (MDL) interactions betweenthe Cache Manager, the SMB server, the file system filter driver, and FAT.There is an error in the Windows NT Cache Manager that may cause datacorruption when the following conditions are true:

  • Windows NT file server (Srv.sys) is running and sharing data on a local FAT-based file system (Fastfat.sys).

    NOTE: This problem does not occur if the server is sharing data on NTFS systems. However, the problem may exist with other third-party file systems or other code that exercises MDL I/O in ways similar to Srv.sys.
  • Windows NT is using a file system filter driver. The filter driver must be aware of the Fast MDL routines and it must filter I/O on the FAT-based file system.

    For more information on file system filter drivers, please see the following article in the Microsoft Knowledge Base:
    ARTICLE-ID: 168513
    TITLE : Windows NT Installable File System Kit (IFS) Description

    NOTE: Windows NT 4.0 does not include any file system filter drivers.
For example, when a filter driver filters data I/O on an SMB server, whichis shared on a FAT file system, the I/O requests that flow from the networksystem through the server, to the filter driver, and into the FAT partitionmay cause data corruption.
An updated version of the Windows NT kernel (which includes Cache Manager)no longer ignores returns from the filter driver that indicate the filterdid not write the data or free the MDL. Cache Manager now takes system-defined default actions.

To resolve this problem, obtain the latest service pack for Windows NT 4.0 or Windows NT Server 4.0, Terminal Server Edition. For additional information, click the following article number to view the article in theMicrosoft Knowledge Base:
152734 How to Obtain the Latest Windows NT 4.0 Service Pack

For your convenience, the English version of this post-SP3 hotfix has beenposted to the following Internet location. However, Microsoft recommendsthat you install Windows NT 4.0 Service Pack 4 to correct this problem.

NOTE: Service Pack 3 must be applied to Windows NT 4.0 prior to applyingthis fix.

Mdl-fix has been superseded by Getadmin-fix. You can find the originalhotfix at the following Microsoft ftp site:

You can work around this problem by using NTFS partitions for SMBserver-based shares instead of FAT partitions or by not using any filesystem filter drivers that filter I/O on top of FAT-based server volumes.
Microsoft has confirmed that this is a problem in Windows NT 4.0 and Windows NT Server 4.0, Terminal Server Edition. This problem was first corrected in Windows NT 4.0 Service Pack 4.0 and Windows NT Server 4.0, Terminal Server Edition Service Pack 4.

Article ID: 179433 - Last Review: 10/07/2013 17:37:35 - Revision: 2.1

Microsoft Windows NT Server 4.0, Terminal Server Edition, Microsoft Windows NT Workstation 4.0 Developer Edition, Microsoft Windows NT Server 4.0 Standard Edition

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