Data Recovery Concept

NTFS Partition Boot Sector

Next table describes the boot sector of a volume formatted with NTFS. When you format an NTFS volume, the format program allocates the first 16 sectors for the boot sector and the bootstrap code.

Byte Offset Field Length Field Name
0x00 3 bytes Jump Instruction
0x03 LONGLONG OEM ID
0x0B 25 bytes BPB
0x24 48 bytes Extended BPB
0x54 426 bytes Bootstrap Code
0x01FE WORD End of Sector Marker

On NTFS volumes, the data fields that follow the BPB form an extended BPB. The data in these fields enables Ntldr (NT loader program) to find the master file table (MFT) during startup. On NTFS volumes, the MFT is not located in a predefined sector, as on FAT16 and FAT32 volumes. For this reason, the MFT can be moved if there is a bad sector in its normal location. However, if the data is corrupted, the MFT cannot be located, and Windows NT/2000 assumes that the volume has not been formatted.

The following example illustrates the boot sector of an NTFS volume formatted while running Windows 2000. The printout is formatted in three sections:

  • Bytes 0x00– 0x0A are the jump instruction and the OEM ID (shown in bold print).
  • Bytes 0x0B–0x53 are the BPB and the extended BPB.
  • The remaining code is the bootstrap code and the end of sector marker (shown in bold print).
  Physical Sector: Cyl 0, Side 1, Sector 1

  00000000: EB 52 90 4E 54 46 53 20 - 20 20 20 00 02 08 00 00 .R.NTFS ........ 
  00000010: 00 00 00 00 00 F8 00 00 - 3F 00 FF 00 3F 00 00 00 ........?...?...
  00000020: 00 00 00 00 80 00 80 00 - 4A F5 7F 00 00 00 00 00 ........J....... 
  00000030: 04 00 00 00 00 00 00 00 - 54 FF 07 00 00 00 00 00 ........T....... 
  00000040: F6 00 00 00 01 00 00 00 - 14 A5 1B 74 C9 1B 74 1C ...........t..t. 
  00000050: 00 00 00 00 FA 33 C0 8E - D0 BC 00 7C FB B8 C0 07.....3.....|.... 
  00000060: 8E D8 E8 16 00 B8 00 0D - 8E C0 33 DB C6 06 0E 00 ..........3..... 
  00000070: 10 E8 53 00 68 00 0D 68 - 6A 02 CB 8A 16 24 00 B4 ..S.h..hj....$.. 
  00000080: 08 CD 13 73 05 B9 FF FF - 8A F1 66 0F B6 C6 40 66 ...s......f...@f 
  00000090: 0F B6 D1 80 E2 3F F7 E2 - 86 CD C0 ED 06 41 66 0F .....?.......Af. 
  000000A0: B7 C9 66 F7 E1 66 A3 20 - 00 C3 B4 41 BB AA 55 8A ..f..f. ...A..U.
  000000B0: 16 24 00 CD 13 72 0F 81 - FB 55 AA 75 09 F6 C1 01 .$...r...U.u....
  000000C0: 74 04 FE 06 14 00 C3 66 - 60 1E 06 66 A1 10 00 66 t......f`..f...f
  000000D0: 03 06 1C 00 66 3B 06 20 - 00 0F 82 3A 00 1E 66 6A ....f;. ...:..fj
  000000E0: 00 66 50 06 53 66 68 10 - 00 01 00 80 3E 14 00 00 .fP.Sfh.....>...
  000000F0: 0F 85 0C 00 E8 B3 FF 80 - 3E 14 00 00 0F 84 61 00 ........>.....a.
  00000100: B4 42 8A 16 24 00 16 1F - 8B F4 CD 13 66 58 5B 07 .B..$......fX[..
  00000110: 66 58 66 58 1F EB 2D 66 - 33 D2 66 0F B7 0E 18 00 fXfX.-f3.f......
  00000120: 66 F7 F1 FE C2 8A CA 66 - 8B D0 66 C1 EA 10 F7 36 f......f..f....6
  00000130: 1A 00 86 D6 8A 16 24 00 - 8A E8 C0 E4 06 0A CC B8 ......$.........
  00000140: 01 02 CD 13 0F 82 19 00 - 8C C0 05 20 00 8E C0 66 ........... ...f
  00000150: FF 06 10 00 FF 0E 0E 00 - 0F 85 6F FF 07 1F 66 61 ..........o...fa
  00000160: C3 A0 F8 01 E8 09 00 A0 - FB 01 E8 03 00 FB EB FE ................
  00000170: B4 01 8B F0 AC 3C 00 74 - 09 B4 0E BB 07 00 CD 10 .....<.t........
  00000180: EB F2 C3 0D 0A 41 20 64 - 69 73 6B 20 72 65 61 64 .....A disk read
  00000190: 20 65 72 72 6F 72 20 6F - 63 63 75 72 72 65 64 00  error occurred.
  000001A0: 0D 0A 4E 54 4C 44 52 20 - 69 73 20 6D 69 73 73 69 ..NTLDR is missi
  000001B0: 6E 67 00 0D 0A 4E 54 4C - 44 52 20 69 73 20 63 6F ng...NTLDR is co
  000001C0: 6D 70 72 65 73 73 65 64 - 00 0D 0A 50 72 65 73 73 mpressed...Press
  000001D0: 20 43 74 72 6C 2B 41 6C - 74 2B 44 65 6C 20 74 6F  Ctrl+Alt+Del to 
  000001E0: 20 72 65 73 74 61 72 74 - 0D 0A 00 00 00 00 00 00  restart........
  000001F0: 00 00 00 00 00 00 00 00 - 83 A0 B3 C9 00 00 55 AA ..............U.

The following table describes the fields in the BPB and the extended BPB on NTFS volumes. The fields starting at 0x0B, 0x0D, 0x15, 0x18, 0x1A, and 0x1C match those on FAT16 and FAT32 volumes. The sample values correspond to the data in this example.

BIOS Parameter Block and Extended BIOS Parameter Block Fields
Byte Offset Field Length Sample Value Field Name
0x0B WORD 0x0002 Bytes Per Sector
0x0D BYTE 0x08 Sectors Per Cluster
0x0E WORD 0x0000 Reserved Sectors
0x10 3 BYTES 0x000000 always 0
0x13 WORD 0x0000 not used by NTFS
0x15 BYTE 0xF8 Media Descriptor
0x16 WORD 0x0000 always 0
0x18 WORD 0x3F00 Sectors Per Track
0x1A WORD 0xFF00 Number Of Heads
0x1C DWORD 0x3F000000 Hidden Sectors
0x20 DWORD 0x00000000 not used by NTFS
0x24 DWORD 0x80008000 not used by NTFS
0x28 LONGLONG 0x4AF57F0000000000 Total Sectors
0x30 LONGLONG 0x0400000000000000 Logical Cluster Number for the file $MFT
0x38 LONGLONG 0x54FF070000000000 Logical Cluster Number for the file $MFTMirr
0x40 DWORD 0xF6000000 Clusters Per File Record Segment
0x44 DWORD 0x01000000 Clusters Per Index Block
0x48 LONGLONG 0x14A51B74C91B741C Volume Serial Number
0x50 DWORD 0x00000000 Checksum

Protecting the Boot Sector

Because a normally functioning system relies on the boot sector to access a volume, it is highly recommended that you run disk scanning tools such as Chkdsk regularly, as well as back up all of your data files to protect against data loss if you lose access to a volume.

For more detailed information see resource kits on Microsoft's web site http://www.microsoft.com/windows/reskits/webresources/default.asp or Microsoft Developers Network (MSDN) http://msdn.microsoft.com

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