Drive Mirroring Can Cause NTFS to Hot-Fix too Often

• Microsoft Windows NT operating system, version 3.1
• Microsoft Windows NT Advanced Server, version 3.1

When the Windows NT mirror support code encounters a sector-read error on one member of the mirror set, it corrects the error if the underlying hardware supports this (true for SCSI devices). After correcting the error on one of the members, the mirror set code returns an informational status to the file system indicating that the data was recovered by reading from the secondary copy.

This informational status causes NTFS to scan both members of the mirror set for faulty sectors (including the secondary member, which the mirror set code did not scan for faulty sectors). If faulty sectors are located on the secondary member, NTFS will map this sector from use at the file system level instead of having the mirror set code map it for use at the hardware level.

There is no data loss due to this error; however, there is the chance NTFS will map sectors for use that could have been recovered by hardware support.