MultiPar VS scorch

but... depending on how much effort you want to spend fixing it I might be able to fix your current corrupt files, especially if the corrupt files are only mildly corrupt I could create a '.par2' file from mine (assuming you are on build 1436.28), then you would use MultiPar (i.e. https://github.com/Yutaka-Sawada/MultiPar/releases ) to scan your files and it will tell me how many blocks you need to fix it and then I could create recovery data with MultiPar. doing this might dramatically lower the amount of data I would have to upload as then you could use MultiPar which will fix your current corrupt files so they match mine identically.

MultiPar is the continuation for Windows https://github.com/Yutaka-Sawada/MultiPar

And this for Linux https://github.com/animetosho/par2cmdline-turbo

* MultiPar supports in-situ repair, which bypasses this problem entirely

To detect bitrot I use dynamix file integrity plugin, it compute Blake3 hash for each file, it is stored as extend attribute. You Can choose which share will be covered. For correction i then use par2 files using multipar https://hp.vector.co.jp/authors/VA021385/ https://github.com/Yutaka-Sawada/MultiPar (Windows only, par2cmdline for Linux. You could compile from source and add it to unraid if you want, i've done it for testing purpose)

And last but not less important - make regular parity files of your healthy important data, and store them somewhere. MultiPar is your best friend. Even if your data gets corrupt, with parity files you can restore it to it's former glory. Some limitations will apply, read the manual.

This is possible with MultiPar https://github.com/Yutaka-Sawada/MultiPar

More sanely, perhaps, get some M-Disc DVDs (if you can find real ones - apparently they're becoming just normal DVDs) and put one file on each, and then run https://github.com/Yutaka-Sawada/MultiPar on it to create parity files. Then store the file, the parity files, and the software you need (MultiPar) on the disc. To be safe, you probably also need to store the DVD burner you used to make it, as those are getting thin on the ground these days.

Note about par2: if one is using a windows system with a nvidia GPU this version of par2 is faster as it speaks CUDA.

For any file repairs use multipar, it's still being updated and has gpu acceleration. https://github.com/Yutaka-Sawada/MultiPar/releases

The method I use is to run scorch every night to compute hashes for new files and check around 12% of old files for hash errors every night. Even if your backup is the same day as a ransomware attack, you will still catch it if the attack hits enough files for one to get randomly scrubbed. Also scorch is designed around making the hash database small and independent from the rest of the system, so you can automate copying it to a bunch of different places.

Lastly, you could just point scorch (https://github.com/trapexit/scorch) at your drives and run it on a cron or systemd timer - just have the script alert you with an e-mail or whatever your preferred method is. Not ideal but probably less work than rebuilding two arrays because you don't like the format of error messages.

If you really care, you can use something like scorch or file-digests to get the hashes of your files and just store that in a text file, recalculating monthly. No need to get fancy with it. Hell, write your own simple script that hashes, outputs to file, and checks previous versions.

Not exactly what you're looking for but close -> https://github.com/trapexit/scorch

Scorch should fit the bill (https://github.com/trapexit/scorch)