DOS FAT32 File Delete Bug RRS feed

  • Question

  • If a file on a FAT32 formatted drive is larger than 4GB - 32,768, that is near the maximum allowed size, and therefore is using the maximum number of 32kb clusters (131,072), and the file is stored in one block (unfragmented), and the file is deleted (as from Window Explorer), DOS fails to make the final cluster available but leaves it marked EOF in the FAT table.  This becomes an orphan cluster that has to be cleaned up by CHKDSK or Norton Disk Doctor to make the disk clean again.  Please fix this probably ancient DOS bug.

    • Changed type pacrosoft Sunday, August 21, 2011 12:01 PM Looking for someone to test and confirm
    Thursday, August 18, 2011 11:39 AM

All replies

  • I tried it out, and it does what you say - leaving the EOF marker at the last position of the FAT chain.

    I used a Windows 7 Pro 32-bit system. The drive was a 600 GB disk with one 32 GB partition formatted as FAT32 by Windows Disk Management. Cluster size is 32 sectors. I used EFCommander 8.0 as file manager. I used Runtime's DiskExplorer for FAT version 4.23 as disk editor. I copied a file with a size of 4,294,958,071 bytes to that partition. It starts at cluster 262,149 and ends in cluster 524,292, thus using 262,144 clusters. After deletion without Recycle, FAT entry 524,292 still contains the value 0x0FFFFFFF (EOF marker). BTW, after copying the file there was also an orphaned EOF marker preceding the file's FAT chain at cluster 262,148.

    Chkdsk had to clean up two lost clusters, 262,148 and 524,292.

    This is a bug that does not put your data at risk but it will clutter your drive with lost clusters.


    Runtime Software, LLC

    Data Recovery

    Sunday, August 28, 2011 3:44 AM
  • It is a general operating system bug I discovered in XP and duly reported here.  It is apparent however that as a DOS error, it is common to 3.1/95/98/ME/2000/XP/2003/Vista/Win7.

    I have no idea whether it is applicable to "Small Business Server" or any of the other highly specialized products taking feedback.

    I do not want to pay support to look into this defect.  I do not want it merely "disclosed".  I want it communicated to MicroSoft and fixed permanently in an update to XP so it does not affect me anymore.  Thanks

    • Edited by pacrosoft Monday, August 29, 2011 11:03 PM spelling
    Monday, August 29, 2011 10:59 PM
  • Best of luck!


    Tuesday, August 30, 2011 6:28 AM
  • Can you use NTFS?

    I can.  For some things.

    I'm hoping a major mod Microsoft employee here will help solve the problem I have with FAT.  And if a current OS, like Win7, has the bug, as Runtime has confirmed, then current and future development will have it in legacy code as well.  Fix for me fixes for everbody forever.  Give me the source code and I'll fix it myself and charge MS for the service ;-)

    Tuesday, August 30, 2011 9:28 PM
  • Noted.

    Tuesday, August 30, 2011 9:38 PM
  • Vegan Fanatic, it is not an answer.  It is a cop out.  You might as well suggest I use a Mac.

    Tuesday, August 30, 2011 10:07 PM