James G. Sack (jim) wrote:
Andrew Lentvorski wrote:
..
The extra bits were to allow the Viterbi detectors to have a longer
stream with which to work. Hard drives actually suck at storing data
and flip bits *all the time*. We have just layered so much error
correction over top that we can recover from extremely large numbers of
bit errors and still produce the original data.
Do you by any chance know any details of the error-correcting magic in
common use? Hamming codes (or related) I assume, but how many errors of
what type are detected? - corrrectes?, etc.
Probably Solomon-Reed error detection and correction. It's very good at
burst errors. Think of a small defective area on the disk. Wikipedia is
your friend here.
There are also white papers on the hard drive manufacturers web sites
that talk about all the stuff they have to do to read a disk to get back
what they wrote.
Gus
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