This harddrive is backed up a few times in a month to another encrypted harddrive via a Raspberry Pi Server in the LAN. On that Raspberry Pi also Nextcloud is installed to allow syncing specific files with other members in the house.
The first harddrive that is connected to my machine directly is also backed up to another drive once or twice a year.
rpi might work too, but slow.
But if you are paranoyed that someone can steal your *photos. From your home.
Then use batteries from old laptop, take them out 3.7V 6 or 8 of them and use few for cloud backup if main power is off and for powerup rpi with cammera for face detection and movement sensors and main electricity inficator and usb 3G or 4G ethernet dongle if that thief will turn off electricity you can get notification via 4G network. If electricity is not turned off you still can get motion detection.
Use rpi gpins to send electroshock to burn that hdd.
Good luck experimenting.
If you're worried about Google (i.e. closing your account) then get some redundancy and use another cloud as well?
If you're worried about your documents being leaked by Google then you probably need to rethink a few things.
It will hold a lot of hard disks...and floppy disks...and zip drives...and Qic tapes...and CD-R's...and DVD's...and SD cards...and USB sticks...and of course paper.
TL:DR; Have several copies on different devices. You might want to invest in a NAS. Extra credit if a copy or two is not in the same place. Recent NAS and Linux distributions support filesystems that can guard against bitrot, which may not be common, but a layered data security approach is best.