My company needs an appropriate physical server configuration for Active Directory authentication that provides hot failover and DR capability. We have approximately 3000 users across 12 sites, plus printers, etc and several hundred application servers.
Current design is for a centralised four clustered server solution (ie 2 x root, 2 x child) which does load sharing and provides failover. In the event of failure of any one server, the redundancy will eliminate any user impact.
However we also require rapid recovery (or preferrably no user impact) in the event that the data centre is lost.
One solution is to split the cluster across two physical locations (which are connected by wideband ethernet), but I am told this is not advisable due to reliability concerns and the additional network traffic would be high.
Proposed solution is to provide two additional servers at the second location (ie 6 servers in total) - but this seems an overkill. Also have separate DNS and DHCP servers which will also require backup devices for disaster recovery.
Any comments, proposed solutions, considerations, etc much appreciated !!!