Solution for Off-site backup

Hi,

since we get fast internet here during the next weeks, an Off-site backup gets somehow realistically.

Since my Parents-in-law also get fast internet, I discussed with them, to be able to host some kind of Off-site backup at their house.

Obviously, it should consume as little power as possible and should be as easy as possible to install.

My current plan would be to get an old Dell optiplex in SFF and put a 18TB HDD into it. The i just have to connect it to LAN and power at their site.

The machine will be always on and connected via WireGuard to my homeserver.

Any better ideas? Anything I missed?