Hope in the right place.. So I've loadbalancer(LB) and two Apaches(A1 & A2) underneath. All of them have public IPs. Now my question is; Client requests a website -> request goes to LB -> requets goes to A1. Now I think response goes the same way back trough LB. So with A1 & A2, LB generates output traffic of both Apaches? Is tha correct, or can I force response directly from Apache (A1 or A2) without touching LB for outbound traffic?
Some insight would be grat, tnx.
normally the traffic will go back through the lb. this is necessary with sticky sessions for example. when you do not want the traffic to go back through the server, you have to send a redirect. but this way, the client will direct the next requests directly to one node and will not know about the other node when this one goes down. so it is definitely your interest that the traffic goes through the lb all the time.
LVS used to support this, not sure if it still does..
http://www.linuxvirtualserver.org/VS-DRouting.html
http://www.centos.org/docs/5/html/Virtual_Server_Administration/s2-lvs-directrouting-VSA.html
You're quick to accept answers. :-)
Yes, in the majority of load balancing solutions all HTTP traffic goes through the load balancer when it goes back 'out' to the client.
Avoiding the load balancer for outgoing traffic is also possible, and is used in some (large) installations. This is called "Direct Server Return" (DSR) or "Direct Routing". Here is a good overview of setting up DSR. Here is a opinion piece on the disadvantages of DSR.
In broad strokes, for 95% of all websites a good load balancer will not a performance bottleneck. Unless you have good reasons, and load balancing expertise available, you should probably not need to play around with DSR.