Document maintaining an offsite backup instance for failover

Some organisations require the option to switch all mission-critical applications to an offsite backup in the event that the primary instance goes down. Please document the basics of setting this up:

1. Install JIRA to a backup server using a development key that is not running
2. Setup a load balancer front end that can test if JIRA is responsive on the primary and backup servers
3. Setup a database backup system that transfers the database contents to the backup server database, eg nightly or hourly
4. Setup a script so that the load balancer will start the backup instance, stop the periodic database transfers and redirect requests in the event that the primary goes down

If there's a better method then we should document that instead.