Is this load balancing or just a redundant online backup? The way I read this was that all traffic goes to one server until it fails and then it flows to the backup. If this is the case and you got a huge influx of traffic it seems like it would crash server 1 and then 2. Or am I misunderstanding it?
1. Having a virtual IP which can move around between two physical hosts, such that it is "always available". (It will clearly go away if both hosts crash).
2. Using HAProxy to route incoming requests, from the single virtual IP, to both back-end webservers.
This means in the expected & typical scenario where both hosts are online both webservers will handle half the load. When one host fails the other will handle all traffic.
Ok, if both load balancers go away it will crash. When master or backup is up, both webservers in background can take all load (100%), because just one loadbalancer will work in one time.
This is both load balancing and a redundant load balancer.
Traffic goes to all the backend web-servers under this scenario, through a single load-balancer device/server.
If that device goes down the secondary takes over.
While if you have millions of requests/sec this scenario wouldn't be quite enough for you, using haproxy with carp/ucarp/keepalived will get you at least 100k connections or more. If you need millions, then you have other problems to worry about as well :).
Basically this will not increase performance, just availability as the main problem with load balancing is that it becomes a SPOF, if it goes down everything is down no matter how powerful web servers you have in background. What will happen if one of those gets huge amount of traffic... I think that it will not go to the backup as CARP should work. But yes it would be nice to test that.
