Saturday, March 31, 2012

What is FDT?

FDT(File Directory Table)is a root zone and a sector following closely to FAT32. Its length is 32 sectors(256 table entries). If long file name is supported, each table entry is 64 bytes. The former 32bytes are long file link specification and the 32 bytes after are file attributes specification including file length, initial address, date, time and so on. If long file name is not supported, every table entry is attribute specification of 32 bytes.

However, the following aspect should be noticed.
FAT 32 has no root directory for directory storage. But FAt16 can store root directory and record subdirectory in data area. The directory entry of directory indicated the root directory address and its length is 0 byte. The directory entry of files indicates the data address.

the characters before DOS7 are E5H, which means deleted. The original cluster of deleted file can be found and data recovery relies on this point.  

Data Area:
Data area is a sector next to FDT, and it extends to the end address of logical disk. It stores all the data. Even file directory is destroyed, the information can be read probably. This is the theoretical basis of disk data.

Up to now, the theoretical part of hard disk data structure has been finished.
Data recovery is to manually find out FAT, directory, relationship between data or to find data directly. There is perfect disk editor simplifying the work. However, intelligentized recovery tools can not recover deleted files by FAT. For example, RECOVERNT may rely on the useing record of Win2000. The possibility of file recovery is very large before restarting. If data is not covered, it can be recovered theoretically. 

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