Replication

I want to do redundancy on my network I am new in this. We have 3 servers in Server Room (Web Server, DNS Server and Mail Server) connection is FDDI (Site A) because of power and connection lost I want to locate 3 same server to other site B, I wantto do replication so that both site have same copy of info and data all 3 server, if the connect is down then on site A then I want site B take over, I want to know which is the best way to do.

Thanks