395736 Failover Load Balancing setup

I need the following done: Let's imagine I buy 4 shared hosting accounts and 2 vps servers. I need a bullet-proof webhosting setup for that. The domain name [login to view URL] will be added to the 4 shared hosting accounts, and webpage will be uploaded to those. The 2 VPS servers will act as a reverse proxy and a load balancer. It should split all the traffic thru the 4 shared hosting accounts. The load balancer should check all nodes every minute using a [login to view URL] hash uploaded to the shared hostings, and if one shared hosting is down or inaccessible, it should not forward requests to that server until it is back up again. The 2 vps servers will be round robined to split the requests. Let me know if you have better idea. Also, the static webpages, like index, pictures should be cached using the load balancer if possible. It would be the best if I could upload the files to the vpses which are static. My site is a PHP site and is working with sessions, so load balancing should support that.