Like all hardware, disk drives have two states - failed and going to fail. Bitrot will also occur with long term storage, whether you notice or not.
A self-healing file system with substantial redundancy capabilities like ZFS is the obvious answer.
However, there are many ways to configure ZFS, and some configurations have better redundancy than others. A misconfigured system would be worse than useless because of the false sense of security. Exactly how many terabytes of data you have also matters for creating the best configuration at lowest cost. Be prepared to spend a little time learning about ZFS before jumping in.