Thanks for your answer.
i don't want dedicated server for WEB / DB / Mail / DNS / Etc...
i want to work as VM in my exists servers just for Cluster configuration
Please see: http://pve.proxmox.com/wiki/Cluster_...ration_(Video)
my main idea is to create better hosting services As close as possible to 100% uptime
there is more benefits to redundancy except uptime
1. better data protection, additional source to data
2. A better option to deal with high load