If you're going to have the 4th box as a backup, instead of power cycling and updating it, consider exercising that backup. Each <period of time> move one syste

If you're going to have the 4th box as a backup, instead of power cycling and updating it, consider exercising that backup. Each <period of time> move one system (since you've described it with identical configurations across all four) to the backup, shutdown (or put into some other idle mode) the now unused system. Repeat. This exercises your failover/restoration process. If you never do that, you don't have a failover/backup process.