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Volume 32, Issue 3

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Monday, 14 January 2013 03:56

Bit Error Analysis of Drives Submitted for Data Recovery

Written by  CLINT FOSTER

Flash media provides many challenges for data recovery personnel, including the ECC (Error Correction Coding) that is implemented within. The ECC technique uses finite fields and their properties to detect and correct a finite number of bit errors in a group of bits. This group of bits for flash media is usually a sector of data bytes, which was usually 512 bytes plus several meta-data bytes, but has been evolving. The data bytes with the associated parity bytes together constitute what is termed a “codeword” or CW. Early flash media devices submitted for data recovery used Reed-Solomon (an ECC method suited for errors that occur in bursts) and could correct up to four symbols. While Reed-Solomon is still used in some drives submitted for data recovery, the vast majority are BCH (Bose, Chaudhuri, and Hocquenghem). With the shift to the new type of ECC also came a shift to higher bit