redundancy questionj

[Jeremy Schubert]

Hello all, I'm new to FreeRADIUS and I'm planning to use Ver 2.2.0 on Ubuntu 12.04 server.
Have 1 central office and 6 remote locations.  
1.  Is it standard to put one server in each of the remote locations which each remote back to the central office server?  Fail-over is a term used in the wiki, is that the same as redundancy?
2.  How stable is FreeRadius...should I consider a primary and secondary server in each remote location?  Or is that over kill?
Thanks,
Jeremy