@NekoKoneko A second system in a secure local with minimal redundancy that can PULL backup data from your production environment at a rate fast enough to keep up. In my case, production is a many node Ceph cluster with flash storage and my backup is a single server loaded with big hard drives in a locked room at work (with approval). Both my house and work have fiber. The backup server pulls data from my production cluster on a regular basis using rsnapshot. It does use RAIDZ1 so I can run my hard drives until they fail without losing backups, but especially because it would take a massive amount of time to rebuild the backup server should I need to do so from scratch. If you have a large catalog of Linux ISOs downloaded via torrent, I might recommend keeping a (backed up) folder containing the old torrent files, that way you can just download them from the source again should you lose everything. Let the community be your backup on those.