Drive-Independent Data Recovery Via Spin-Stand Imaging

摘要

There is currently no viable means for data recovery from drives which have suffered damage and cannot be resuscitated by using standard software, firmware, or part-replacement techniques. In the paper, an ex-situ technique for drive-independent data recovery based on spin-stand imaging is presented. In this spin-stand imaging based technology, the disk is removed from its native drive, placed on a spinstand, and scanned with a magnetic head. After raw signal acquisition, bit detection, data decoding, and sector mapping, the otherwise unrecoverable data can be retrieved. Raw data acquisition involves preliminary mechanical track-centering [1], dynamic track-following [2] as well as track-following based on feedback from preexisting servo bursts on the disk platter [3]. Bit detection includes special filtering and techniques for intersymbol interference removal [4]. Data decoding entails de-interleaving, run-length limit (RLL) decoding, descrambling, and correction of errors using error correction codes (ECCs). The entire decoding process is by and large performed without prior knowledge of the scrambler and the ECC encoding, but rather using proper "interrogation" of hard disk drives. This "interrogation" makes extensive use of linearity of scramblers and Reed-Solomon ECCs and can decipher both the initial states and the scrambler and generator polynomials of scramblers and ECC codes. After the decoding is finished, the recovered data sectors are then assembled into the correct sequence to form complete readable files. Fig. 1 is a graphical illustration of the sequence of steps involved in spin-stand based drive-independent data recovery.