You absolutely do not want to use Round Robin DNS. The main issue is that it cannot balance load with any kind of intelligence, and it doesn't take into account DNS caching on the client side. DNS is just not meant to do Load Balancing. This technology is deprecated and what you really want to use is a Server Load Balancer (either Appliance or Software, but I really recommend an Appliance if you care about performance).
What happens is this:
- You set up a domain name, and tie its IP Address to your Server Load Balancer (SLB) public IP Address, which is called a VIP (Virtual IP Address).
- When the SLB receives a connection request, it will establish the connection between the client and itself. Your clients will then send data inside that connection (an HTTP request in your case). Some SLB can redirect the data stream to a specific server based on the type of request, but that's a bit advanced for now.
- The SLB will then establish another connection between itself and another server. It will choose the server from a pool you specified. This is where you specify the IP Addresses of all your servers. Based on the Load Balancing rules you defined, it will choose one server or the other. Some possible rules are Round Robin (it will send the first user to the first server, the second user to the second server, and so on), Weight (if server 1 is twice more powerful than server 2, it will send twice more users to the first server), Load (if server 2 is more loaded than server 3, the SLB will send to server 3 in priority), and some others.
- A popular way of improving performance is to use the SLBs to do the SSL termination between itself and the client, and then use clear text between itself and the server. This way you don't need SSL on your server (saving tons of performance), which most of the time is fine because you are on a private, trusted network; while still keeping the level of security needed on the public (Internet) network.
Some popular SLB vendors are F5 (my personnal favorite, but that's just me, and they tend to be more expensive - for good reasons, but that's also my opinion), RadWare, Cisco and Juniper.