Microsoft KB Archive/152667

= NTFS Uses CPU 100% While Allocating File Space =

Article ID: 152667

Article Last Modified on 11/1/2006

-

APPLIES TO


 * Microsoft Windows NT Workstation 3.5
 * Microsoft Windows NT Workstation 3.51
 * Microsoft Windows NT Workstation 4.0 Developer Edition
 * Microsoft Windows NT Server 3.5
 * Microsoft Windows NT Server 3.51
 * Microsoft Windows NT Server 4.0 Standard Edition

-



This article was previously published under Q152667





SYMPTOMS
You are copying large files (of 50 MB or more) from a computer running Windows 95 to a computer running Windows NT installed. You are moving the files with a drag-and-drop operation, using the Network Neighborhood tool or the My Computer tool in Windows 95. Windows NT CPU use increases to 100 percent, resulting in performance degradation and client disconnections.



CAUSE
The Network Neighborhood and My Computer tools in Windows 95 issue an SMBwrite of zero bytes at a file's new end-of-file (EOF) offset before actually writing data to the file. On large file systems that are highly fragmented, copying a large file can cause the Windows NT file system (NTFS) to use 100 percent of the CPU for an extended period of time. This can result in other threads being starved of CPU time, causing performance degradation and client disconnections.

This problem exists whenever a write of zero bytes occurs at a large offset beyond EOF on a highly fragmented file system as NTFS tries to allocate space to satisfy the request.

Using COPY/XCOPY from the DOS-PROMPT or copying to a FAT partition does not result in this behavior.



STATUS
Microsoft has confirmed this to be a problem in Windows NT versions 3.5, 3.51 and 4.0. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

Additional query words: prodnt

Keywords: kbprb KB152667

-

[mailto:TECHNET@MICROSOFT.COM Send feedback to Microsoft]

© Microsoft Corporation. All rights reserved.