Required configuration setting for server reduandancy in vijeo citect 7.20 scada

Dear All,
i m currently working on vijeo citect scada 7.20 and i need to confiure server reduandancy in our project . so plz tell me the required setting for server redunadnccy in vijeo citect scada 7.20.because i didnt find good help from schinder site.
Thank you.

Redundancy in Vijeo Citect can be defined at many different levels.
<LI class=pSmartList1 value=1>I/O Server Redundancy <LI class=pSmartList1>Alarms, Reports, and Trends Server Redundancy <LI class=pSmartList1 value=2>I/O Device promotion <LI class=pSmartList1 value=3>Redundancy and Persistence <LI class=pSmartList1 value=4>Data Path Redundancy <LI class=pSmartList1 value=5>Network Redundancy Refer Citect help itselfwhich is best. Refer the topic named " Building redundancy into your system"