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NTFS Performance Problem with Many Files

Article ID: 130839 - View products that this article applies to.

This article was previously published under Q130839

SYMPTOMS

An NTFS volume containing a very large number of files may exhibit degradation in performance when you create new files.

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In an effort to provide consistently good performance, the Windows NT file system (NTFS) reserves a portion of disk space for use by the file system itself. In situations where very little disk space is available, Windows NT may need to release some of this space in order to allocate space for user files. In the vast majority of cases, this algorithm works well. In one specialized case, however, it is possible for the algorithm to actually degrade performance by a significant amount.

The worst case occurs if all of the following conditions are true:

NTFS is formatted with a smaller cluster factor than the default.
Less than 1/8th of the total disk space is available.
The volume has never had more files on it at one time than it has now.

The problem described here only occurs when you create new files, and the total number of files is being increased to a number greater than ever before. The magnitude of the performance degradation depends on the history of file creation on the volume. It is possible to observe degradation with as few as several hundred thousand files. It is also possible to create more than two million files on a single volume without observing significant performance degradation depending on the pattern of file creation.

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WORKAROUND

To work around this problem, reduce the total number of files on the volume or reformat the volume. To minimize the impact of the problem when a very large number of files is required, attempt to create the smaller files first before most of the disk space is already in use.

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STATUS

Microsoft has confirmed this to be a problem in Windows NT version 3.5. A fix to this problem is in development, but has not been regression-tested and may be destabilizing in production environments. Microsoft does not recommend implementing this fix at this time. Contact Microsoft Product Support Services for more information on the availability of this fix.

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