Intermittent File Corruption Problem

• Microsoft Windows NT Workstation version 4.0
• Microsoft Windows NT Server version 4.0

SYMPTOMS

If files are rapidly accessed on a Windows NT file server, intermittent data corruption may occur. Microsoft Internet News Server data files may exhibit these symptoms. The problem is more likely observed on a multiprocessor system.

CAUSE

If an application performs a write-extend of a file, the cache manager read-ahead thread is also reading the current last page of the file as part of a larger read. The read-ahead thread issues the read, and the write is blocked while the read completes. Because of a timing problem that may occur, the memory manager wakes the write thread associated with the I/O operation. This thread will place null characters in the last page that is beyond the current file size and then write the new data into the page. The read thread wakes up and also zeroes the last page after the write thread has written the new data. The update to the page is lost and null characters are appended in the file instead of the data that should have been committed for the I/O operation.

STATUS

Microsoft has confirmed this to be a problem in Windows NT version 4.0. This problem was corrected in the latest Windows NT 4.0 U.S. Service Pack. For information on obtaining the Service Pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

   S E R V P A C K