Reassessing the roles of Domino servers and current architecture

first an overview of my clustered enviornment:Two Domino servers. Our main Administration server which performs all mail routing tasks, as well as serving all databases and “TeamRooms”. The other server, its cluster partner waits in abayance for a failover ( a crash of the Admin. server, not loadbalancing )

We are going to be adding a SameTime Domino server. As well as Instant messaging we were going to assign it some more labor intensive tasks, ie. Domain Cataloging (Domidx) for the databases on Admin. server, as well as making it an application server.

My questions are in the planning for its role within the current architecture, and providing redundancy for it.

Can anyone recommend reading in growing and reassessing your Domino enviornment? Or even provide feedback/opinions.

Thanks much.