it's one server as master (write) and one as slave (read-only). you also must do backups, but using this approach it will be more safe than only backups. later

it's one server as master (write) and one as slave (read-only). you also must do backups, but using this approach it will be more safe than only backups. later, you can setup to when one server crashes [master or slave], automatically setup a new server and copy the data.