Custom Forward Error Correction?

[rp0]

I'm planning on using M-DISC to archive a few terabytes of data. I am worried about the disc getting corrupted and becoming unreadable (scratches, deterioration, or whatever) after many years.

My idea is to invest in more upfront processing to compute and insert parity blocks onto the disc for forward error correction. I have software that operates on chunks of data and spits out some parity bits, and the same software can reverse the process and recover bit errors. I realize this will take up more space on the M-DISC (having to include more parity bits compared to a normal burn), but it's worth it to me.

Will this method work? Will it actually improve my chance to recover the data?

I'm not sure what error checking methods are already included in reading/writing discs. I'm assume there must be something because I've had times when Windows will be completely unable to load a disc. I'd like to know if there is a "raw data mode" (is this what an ISO format is?). That way, even if there are bit errors (ie Windows won't load it), I can still just ask ImgBurn to read out whatever bits it can, and then I would run my own parity software and attempt to recover the data myself.

[dbminter]

Personally, I would see creating parity error recovery on a disc as a waste of time.  If the disc has scratches, etc. that make it difficult to read files, then reading a smaller file like some kind of parity recovery would make it even more difficult as small data would be more affected by a larger scratch.

[LIGHTNING UK!]

I see no problem with doing this.

Just allow youself 10, 20, whatever% of the disc space for parity files of whatever you want to burn.

So split your data (collection of files) in ~20gb chunks, generate 4gb worth of parity files and burn the whole lot to a 25gb disc.

Going back many years, I know par and par2 files were heavily used on newsgroups... they probably still are.

[dbminter]

PAR and PAR2 were still in use about a decade plus ago, when I last had access to newsgroups.

 

They still even use NZB's to this day, from what I've heard. 

[rp0]

Great to hear that it's at least plausible. I've had issues with Windows trying to read discs in the past (it seemed like it was all or nothing).

Does imgburn have a feature to just extract whatever bits are on the disc, corrupt bits and all?

[LIGHTNING UK!]

You can have it ignore unreadable sectors (and zero fill the file) when using Read mode, yes.

Once the stuff is on the disc though, you could use any old recovery type software to try and read as much of the disc as possible.... then rely on your par/par2 files to fix anything.