Hard disk data recovery knowledge Part 1 - The working mechanism of system introduced in brief

This part of the original is the most important chapter, considering the relationship between length, a large number of truncated.

(1) DOS (DOS compatible systems) hard drive the structure of the data

DOS disk system, can according to the logic of the concept of physical space division management, different partition can load different OS system.

Beckoned to the following:

Hard drive space

The first sector | division 1 | 2 | 3 | division division division four

The Lord boot sector | boot sector | boot sector | boot sector | boot sector | The area public | each partition relatively independent, can install different operating system.

The partition of FAT structure every division have independent boot record, FDT table, FAT table, etc. At the same time, the system has a most important master boot record. In the column 1 0 0 face sector, in the future, we use CYL representative column, SIDE represent surface, SEC representative sector. The following a FAT structure division of the diagram.

Reserves-the disk parameter table, DOS boot record

Control areas-FAT table 1 and table 2 FAT root directory area

Data area-data area

The following simple introduce important part:

The master boot record and said the Lord partition table, MBR and so on: MBR accounted for a sector, in CYL0, SIDE0, SEC1, area code and data area by composition. One at one end of the standard code area is program, complete the BIOS since lifted to OSBOOT work between, for OS start the final preparations. Standard code area can be made by FDISK/MBR reconstruction, but for many of the guide system standard MBR, will be the operation damage. MBR data section division of the record.

System sector: CYL0, SIDE0, SEC1-CYL0, SIDE0, SEC63, a total of 62 fans Area and say BOOT area guide area: CYL0 SIDE1, SEC1 this is, we in the past say the DOS lead The area. Also accounted for a sector.

File distribution table and say FAT: is occupied the records of the place and connections. Generally has two FAT table, have backup role. FAT12, FAT16 first FAT table in general are 0-1-2, the first FAT table in FAT32 0-1-33. Because FAT table records document takes up the sector of the connection place, if two FAT table is broken, the consequence is unimaginable.

Because of the length of the table with the current FAT division related to the size of the FAT2 address is so needed to calculate. The ROOT directory area (ROOT, FDT) : here in the ROOT directory records the directory file such as item, ROOT zone in FAT2 with behind.

Data area: with the ROOT zone back, this is the data content. In fact, MBR, implied sector, BOOT area, reconstruction were easy. Data recovery, the key is that recover the data files. Because the FAT table record files in hard drive takes up the sector linked list, if two FAT table is completely damaged. So recovery files, especially take multiple discontinuous sector file quite difficult.

(2) the master boot record on simple explanation

The master boot record is the starting point of the hard disk guide, about code area not say more, its data area, more important is the symbol of 2, 80 H and 55 AA, 80 H general in the migration in BE 1, 80 is a sign of division activation mark said system can guide and the whole partition table can only have a 80 mark. The other one is at the end of the 55 AA mark, used to show the master boot record is a effective record. In addition, each division own guide records, is also to 55 AA end. This is we find the sign of division. We introduce how to at the back of the master boot record, gives a complete partition table example, everybody can be controlled to check. Data area, with 10 H byte represents a partition, up said four division, separately from 1 BE, 1 CE, 1 DE, 1 EE started, we are behind a partition table corresponding address of meaning. We can analyze the corresponding division of the situation.

800101000 BFEBFFC3F00-00007 E86BB00

(1) (2) (3) (4) (5) (6)

(1) : activate marks, 80 said may guide the partition

(2) : the head no. In the division began 01, the start of the sector, 01, for the start of the cylinder number is 00, for a start, the sector for 2 into the six, and the start of the cylinder number is 2 into the 10, so the number of bytes sector high two will be added in the cylinder high number two.

(3) : zoning system type FAT32 (0 B), is FAT12 01, for FAT16, 06 for BIGDOS, 07 to NTFS,Other see partition type table.

(4) : 254,, and the end of division head, no. 63,, and the end of partition sector division over 764 cylinder

(5) : the first sector of the relative sector no. 63

(6): total sector number 12289622