I use git-annex to do pretty much what you're describing. It takes some getting used to, but it's much better than your suggested method of rsyncing to some USB

I use git-annex to do pretty much what you're describing. It takes some getting used to, but it's much better than your suggested method of rsyncing to some USB sticks. Under the hood it's basically doing that, but everything's SHA-256 checksummed so you can check its validity, and all copies of your data also sync metadata telling them who else has copies, it's easy to enforce policies that some content must have >N copies etc.