Sometimes it occurs that I get storage discs that suffered of keen hands of an unskilled "expert". Some days ago I received a HDD Maxtor Ares 64K for data recovery from a town of Mozdok.
The disc had a common error due to the microprogram failure. A repairman was found at their town. He made a try and said that he could not cope with a problem. When I got a carrier, it turned out that overhead information of another hard drive together with strange defect lists and adaptive information was completely overwritten on the storage disc.
The alternative, i.e. the factory default SA was also exposed to severe intervention. After such resolute actions the drive displays readiness, is correctly defined in BIOS and displays a descriptor (with a strange serial number). The data problem is sadder. The data behave as though they both exist and do not exist at the same time. It means that mbr and boot is normal but in the first mft sector, named in boot another sector is displayed instead of mft record.
The so called translator shift is at present. What is it and why does it happen? I'll try to explain. Just imagine data as a line with 0-lba at its beginning and the last lba sector at its end. When a disc comes off the conveyorized assembly, the factory self-testing procedure helps to discover all possible defects. Among all procedures, as a result of self-scanning defect lists are created. Even at the factory it is impossible to produce an ideal surface, especially at the higher density recording used for modern hard drives. I will not say about nuances of track, zone and other defects, we just take into account presence of faulty sectors. It is clear, that each HDD, even of the same series, has its own defects. One disc has more faulty sectors, another disc has less of them, and they are located in different places. In the figure you can see 3 on the disc "А" and a faulty physical sector 6 on the disc "В". Logical marking misses a faulty sector, and the second logical sector will be a physical one "in a sector". This is called translation.
Logical translation forming in HDD
If we overwrote the defect table of carrier "В" to the disc "А", we will get a translator shift I said before starting with LBA 2. The faulty physical sector 2 is not excluded and is taken as LBA 2 (but it will be unreadable as it is faulty), the LBA 2 sector is taken as LBA 3, LBA 4 disappears, as it is hidden in the defect table, and so on and so forth.
Solving such a quest is a very hard task. Data recovery cost in such a case increases in several times.