We have two sites for our servers. One is up and live 24/7. the other has no servers turned on. Our website A record points to our live servers in the primary site.
Question - if our servers go down we will boot up the alternate site servers. we will change DNS where the A record points to. Is this a good strategy? We don't get thousands of hits (field reps use our website, not public). We would need TTL to be low enough ahead of time that we can make change in DNS through our registrar (Register.com) and assume the field reps will see those changes 15 minutes later when they start querying our website again.
We can't build new servers to run BIND. Register.com is where we control the records. We don't want both IPs published at the same time because our other site is always down (the firewall is up, but no servers). We don't want users being directed to the IP of the DR site while it's not up and running.