Among other things, I’m running a small Nextcloud instance on my home server and over time, data somewhat piles up (especially photos). My main storage is sufficiently sized & redundant for now, but I wonder how I am supposed to do a serious backup: The moment will come where the backup’s size will exceed any reasonly prized single drive. What then?

Of course I can just buy another disk and distribute the chunks, but that’s manual work - or is it not? At least rsync has no builtin option for that.
Using a virtual, larger file system spanning among multiple drives looks like the easiest option, but I doubt it’s a good idea for a reliable backup - if one disk fails, all of the backup is gone. On the other hand: That’s true for the distributed chunks as well.

What do you people do? Right now I don’t have to bother as my data fits on a single device easily, but I wonder what in theory & practice is the best solution.
Regards!