Use HAProxy or Nginx to Load Balance between VPS

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http://serverfault.com – I want to load balance + failover backup multiple vps webservers hosted on different providers. I heard that for HAProxy you need multiple server under the same subnet, plus a shared (virtual) ip address between load balancers. But it's not possible in my case cause every VPS is on different node/network. Is there a way to use HAProxy in this kind of setup ? ( Please explain how briefly, I don't want to hear your "YES" answer ) What about NginX? Is it possible to achieve same result with Nginx ? (when servers are located on different nets) I know about Round Rubin DNS, but it doesn't pro (HowTos)