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A chkdsk /r on a Windows XP NTFS system partition revealed bad clusters in a file. chkdsk reported "bad clusters in file xyz have been replaced" (translated). The filesystem is stored on a plain SATA disk (no RAID).


If the error occurred during a read, NTFS returns a read error to the calling program, and the data is lost.

Ok, I guess the file is corrupted... really?


When an unreadable sector is located, NTFS will add the cluster containing that sector to its list of bad clusters and, if the cluster was in use, allocate a new cluster to do the job of the old. If a fault tolerant disk driver is being used, data is recovered and written to the newly allocated cluster. Otherwise, the new cluster is filled with a pattern of 0xFF bytes.

What is meant by "fault tolerant" disk driver? A RAID system? Is there any means to determine if chkdsk restored the file without data loss or do I have to resort to using a hex editor to search to file for a 4 kB bloc filled with 0xff? I am pretty sure the file is corrupted and I can easily restore it from backup, but I would like to now if there is a definitive answer.

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migrated from Mar 13 '11 at 19:15

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If you have a backup, then simply restore the file and compare with the one that chkdsk repaired. – Greg Hewgill Mar 13 '11 at 19:14
Seems like the Microsoft documentation is incorrect: I found a zero-filled 4k block by comparing the file relocated by chkdsk with the restored one from backup (no 0xff filling). So my assumption was correct, the file is in fact corrupted. – georg Mar 13 '11 at 21:31

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