As a photographer with over 100k clicks on three bodies, I have just over 2 TB of my own photos on a dedicated drive. I have a two step backup system:
1) With a USB "drive toaster", perodically back up my files to a raw drive, mark it with a sharpie, and put it on the shelf in a different part of the house.
2) About twice a year, ghost my primary storage to a brand new drive, install the new drive in place of the old drive, mark the old drive with a sharpie, drive it over to a friend's house and put it in his fire safe. This serves as my hardware refresh and disaster recovery.
The older drives from previous backups in his safe are repurposed for music/movie storage, or used to rebuild PCs for other family members.
Were I really serious, I'd also mirror my primary storage, but at some point you have to say "this is good enough". Besides, any photos I've published exist on various websites, and I can always fetch copies from there in an emergency.