Error Message:

Fixing mirror copy of the security descriptors data stream.

Explanation:

Each file on an NTFS volume is listed as a record in a special file called the Master File Table (MFT). The first record in the table describes the MFT itself and the second record is an MFT "mirror" record. If the first MFT record is corrupted, NTFS uses the second record to restore the primary MFT file and vice versa. NTFSCHK is currently using the primary MFT to fix the mirror copy of the security descriptors data stream file ( $SDS). No user action required.