Deleted Disk Space Not Released on Converted NTFS Volume

• Microsoft Windows NT Workstation version 3.51
• Microsoft Windows NT Server version 3.51

SYMPTOMS

If you copy a large file to a nearly full disk, delete the file, and then copy another large file to the disk, the second copy attempt may fail. This problem occurs even though the system reports adequate disk space is available for the second file.

This problem only occurs on computers that were upgraded to Windows NT 3.51 from a previous version of Windows NT, and on which the disk volume was converted to the Windows NT file system (NTFS) during or after the upgrade process. This problem occurs on uncompressed volumes, and will not occur on volumes that were formatted for NTFS prior to installing Windows NT 3.51.

CAUSE

When you copy then remove a large file from a nearly full NTFS partition, you may create free space between the beginning of the disk and the Master File Table (MFT). Because NTFS starts looking for free space at the MFT, NTFS does not see the free space after the file is deleted.

RESOLUTION

To work around this problem, install Windows NT 3.51 in a new directory.

To correct this problem, install the latest U.S. Service Pack for Windows NT version 3.51.

STATUS

Microsoft has confirmed this to be a problem in Windows NT version 3.51. This problem has been corrected in the latest U.S. Service Pack for Windows NT version 3.51. 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

MORE INFORMATION

When NTFS is looking for free space on the disk, it scans through a bitmap of the disk that identifies the state of each block on the disk (free or in use). The scanning process starts at the MFT rather than the beginning of the disk. If free space exists before the MFT, the space is not found during the scanning process. If the disk was formatted for NTFS, there are no files between the start of the disk and the MFT. However, if the disk was converted to NTFS, then files can exist between the beginning of the disk and the MFT. Once those files are deleted, free space exists between the start of the disk and the MFT. Because the scanning process starts at the MFT, free blocks before the MFT are never be allocated to a file.

For additional information on NTFS and Master File Table, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q101670
   TITLE     : Transaction Log Supports NTFS Recoverability