Re: storing files on an error-prone medium

From: no name (noone_at_linux.local)
Date: 09/13/04


Date: 13 Sep 2004 02:07:41 -0500

ebenONE@tampabay.ARE-ARE.com.unmunge (Hactar) tried to express:
> I recently learned that the error rate on DVD-RWs is something like 1 error
> per 1E9 bits. That works out to around 37 errors per 4.7 GB disc. While
> that may be acceptable for movies, it's definitely not OK for programs or
> most compressed files.

It is quite OK when you consider that the raw bit error rate doesn't take
into account the ECC (error correcting codes) that are written for each
data block on the media. Most media will have some bit errors so the
firmware adds ECC to the data stream so that those rogue bits are
transparently corrected.

Each data block is compared to a (checksum) and if the values don't match
then single bit errors are transparently corrected using some math that
is beyond my ability to discuss rationally at 3AM.

Don't worry about it, and if you must worry about it then write your own
error correcting code...search the comp sci literature for ECC and CRC



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