I've considered using Round-robin DNS failover, but due to various levels of DNS caching, you run the risk of old records pointing to a down site.
If I own my own address space and AS number, in data centre 1, I can announce my 1.1.1.x/x network to the world from my router and everyone can hit the load balancer at 184.108.40.206, life is peachy. I could then have in another data centre, the same set up, and the router there also announces my IP space and AS number to a different upstream provider there. Users will obviously hit the closest set-up to them based on the AS-PATH and other metrics from BGP in their local ISPs network.
Now, lets pretend something terrible happens at data centre 1, and router 1 goes offline, my IP space and AS are no longer announce there, and all traffic will fall back to solely data centre 2, for traffic to 220.127.116.11 (load balancer). Do people do this, is this a ridiculous idea? Have I missed something blindingly obvious about why I shouldn't do this? Is this just not practical, or a genius plan?