Summary of Windows NT NTFS and FTDisk Data Recovery

ID: Q129038

The information in this article applies to:

Microsoft Windows NT Workstation version 3.5
Microsoft Windows NT Server version 3.5

SUMMARY

FtDisk, the Windows NT fault tolerant driver, provides the mechanisms for redundant data storage, volume management, and dynamic data recovery.

MORE INFORMATION

Dynamic data recovery is only available on SCSI drives. FtDisk works between the physical disk drivers and the file system drivers, and works with all the supported files systems (FAT, HPFS, and NTFS). Windows NT file system (NTFS) is the only file system with built-in data recovery mechanisms.

The table below lists the data recovery options available when you have FtDisk installed on an NTFS drive.


          SCSI Drive with       Non-SCSI drive or      Any type of
          spare sectors         no spare sectors       disk drive

--------------------------------------------------------------------------


Fault     1. FtDisk can         1. FtDisk can          N/A
Tolerant     recover data          recover data
Volume    2. FtDisk uses        2. FtDisk sends data
             sector sparing        and a bad-sector
             (replaces sector)     error to the file
                                   system
          3. File system is     3. NTFS performs
             unaware of            cluster remapping
             the error

Non-Fault 1. FtDisk cannot      1. FtDisk cannot       1. Disk driver
Tolerant     recover data          recover data           returns bad
Volume                                                    sector error
                                                          to file system

          2. FtDisk sends       2. FtDisk sends        2. NTFS performs
             bad-sector error      bad-sector error       cluster remapping
             to file system        to file system
          3. NTFS performs      3. NTFS performs
             cluster remapping     cluster remapping
             DATA IS LOST          DATA IS LOST        DATA IS LOST
---------------------------------------------------------------------------

Fault tolerant volumes include mirror sets (RAID 1) and stripe sets with parity (RAID 5).

Note: If FtDisk finds a bad sector on a fault tolerant volume, and the physical disk supports spare sectors, and has spare sectors available, FtDisk replaces the sector. This is true for all tree supported file systems (FAT, HPFS, and NTFS); the file system remains unaware of this mechanism.

For more information on NTFS, see "Inside the Windows NT File System" by Helen Custer.

Additional query words: prodnt ft ntfaqset

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