I’m trying to plan a better backup solution for my home server. Right now I’m using Duplicati to back up my 3 external drives, but the backup is staying on-site and on the same kind of media as the original. So, what does your backup setup and workflow look like? Discs at a friend’s house? Cloud backup at a commercial provider? Magnetic tape in an underground bunker?
I’ve always understood 2 as 2 physically different media - i.e., copies in different folders or partitions of the same disk is not enough to protect against failure of that disk, but a copy on a different disk does. Ideally 2 physically different systems, so failure/fire in the primary system won’t corrupt/damage the backup.
Used to be that HDDs were expensive and using them as backup media would have been economically crazy, so most systems evolved backup media to be slower and cheaper. The main thing is that having /home/user/critical, /home/user/critical-backup, and /home/user/critical-backup2 satisfies 3 copies, but not 2 media.