In my setup I have everything on a (large) server in a colo, with and exact copy on a second server, with the databases in master/slave. Every two years I buy a

In my setup I have everything on a (large) server in a colo, with and exact copy on a second server, with the databases in master/slave. Every two years I buy a new server and swap the oldest one out. When the master server fails, I can run script to cut over with very minimal manual interaction. I have not had to use the script in 10 years, and only experienced one outage when the datacenter had a blip. But... it's really hard to not worry about it occasionally, even after 10 years.