I was thinking that IPVS wasnt allowing to put nodes on load balancers because of ip forwarding.
The problem is not really with HD i/o (Xen is on a partition) but for some reasons when I do CPU benchmarks I get poor results with Xen compared to a straith install.
Since software load balancers (such as ldirectord + heartbeat) use very little ressources, I think its better to put it directly on the first two webserver nodes 1)to save on hosting (less boxes) 2)less management and 3)better use of load balancers ressources.
Im slowly working on an updated version of : http://howtoforge.com/the-perfect-lo...04-hardy-heron
Here are the points I will improve :
2)No more virtualization for better performance
3)Storage in a "cloud" instead of rsyncing files between servers (eg http://blogama.org/node/78
4)Single management interface (ISPConfig 3??)
I did not test it yet but I believe it would be possible to use ISPConfig 3 to control a load balanced + HA cluster with very little modifications...
Will keep you updated
btw cookie expire pretty quickly on howtoforge... anoying with long posts...