WM 6.5 IS clustering with external load balancer

I am planning to build a IS cluster of 2 webMethods 6.5 servers for failover reasons and will be using an external load balancer (foundry) for load balancing between these two servers. Now I have some doubt on following few situations

  1. Say one of the server has failed means the server or the port has somehow gone down. Now will the external load balancer be able to detect this failure and divert the traffic to the other server automatically? OR the load balancer will get the error response back from failed IS and return the response back to the client ?

  2. In case the server is up but due to some problem (say no space left) the server is unable to process the request. In this situation willl the second server in the cluster pick up the request and process it?

Can anyone please clarify these doubts. This is very urgent for us as the configuration needs to be done in production very soon.