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# Large File Copies May Fail After 4 Gigabytes in Windows NT

Article ID: 104181

Article Last Modified on 3/15/2004

APPLIES TO

- Microsoft Windows NT Advanced Server 3.1
- Microsoft Windows NT Workstation 3.1
- Microsoft Windows NT Advanced Server 3.1

This article was previously published under Q104181

## SYMPTOMS

When you copy a large file [greater than 4 gigabytes (GB) in size] between two Windows NT computers, the file may become corrupted on the destination computer.

## CAUSE

This is caused by a problem with the Windows NT network redirector where, in extending the file after copying just less than 4 GB, the redirector actually truncates the file by using only the low part of the LARGE_INTEGER file size. The next write then time-outs because the server has to zero-extend the file, which takes more than 45 seconds.
NOTE: Even if the time-out didn't occur, all of the data between the truncation point and 4 GB would be lost, which would be even worse.

## STATUS

Microsoft has confirmed this to be a problem in Windows NT and Windows NT Advanced Server version 3.1. This problem was corrected in the latest U.S. Service Pack for Windows NT and Windows NT Advanced Server version 3.1. For information on obtaining the Service Pack, query on the following word in the Microsoft Knowledge Base:

`SERVPACK`

Additional query words: prodnt

Keywords: kbnetwork KB104181