I did this, NAS to NAS as storage density improved, with rsync checksums on. Years into this I noticed a thumbnail that didn't render, found I couldn't open th

I did this, NAS to NAS as storage density improved, with rsync checksums on. Years into this I noticed a thumbnail that didn't render, found I couldn't open the original. Looked around, there were quite a few. Ran a RAW + JPEG error detection script: on the order of 10^1 - 10^2 of photos were no longer valid out of on the order of 10^5 - 10^6 photos. Turns out rsync verifies on the way, not after write.