> How would you encode a petabyte (for a starter) with LDPC/Turbo?

I'm fairly certain that particular problem you're asking for is solved by "fountain LDPC codes", and can't be solved by RS by any methodology.

RS is limited to its block size (in this case, 2^20 sized block), which can be "extended" by interleaving the codes (with various kinds of interleaving). But interleaving a petabyte of data is unreasonable for RS.

I admit I'm not hugely studied in practical codes, mostly just got the college-textbook understanding of them.