I have a single external HDD that I'd like to use as storage for data that's not read/written very often. I'd like to make this storage resilient against faults that might occur.
ZFS apparently supports copies=2, where each bit of information is stored twice on the disk, preventing bad sectors from leading to data loss.
Question 1: Is it worth it to use this type of single disk redundancy? What are the relative risks of partial drive failure to total drive failure?
Question 2: Two copies seems excessive for my use case. Is there a way to have, say 30% redundancy, like Parchive does but on the filesystem level? Ideally this redundancy would be a lazy process, where the filesystem returns as soon as it has written a single copy, and writes the redundancy bits when it's idle.