If you have three copies then you can automatically heal from any single sector going bad, and semi-automatically heal from a sector going bad in the same spot in two copies at once. Or you could make five copies even.
> (And btw, parity doesn't protect you from bitrot forever, only for like a decade or two)
Based on what settings and what environment?
By the time you're losing a large percentage of your sectors, you're probably losing everything regardless of format. You don't use file formats to protect from entire disks or tapes failing.
Also, if you set up paranoid levels of parity you can recover a perfect image even when a RAW file would be covered in gaps and noise, while still being a lot smaller.
Let's assume I'm willing to spend the dollar more on storage for both options.
I can either store one copy of a RAW, or I can store an unholy ball of parity that's exactly the same size.
The unholy ball of parity can lose up to 90% of the data and still be completely recovered, giving you a very high quality image, but if you lose more than 90% you get nothing.
A RAW image degrades more and more as you lose data, and if you lose 90% it's going to be useless anyway.
I'll definitely pick the compression+parity option.
> (And btw, parity doesn't protect you from bitrot forever, only for like a decade or two)
Based on what settings and what environment?
By the time you're losing a large percentage of your sectors, you're probably losing everything regardless of format. You don't use file formats to protect from entire disks or tapes failing.
Also, if you set up paranoid levels of parity you can recover a perfect image even when a RAW file would be covered in gaps and noise, while still being a lot smaller.