We're running Exchange 2007 using two servers and employing Standby Continuous Replication. Both servers are running the same roles: CAS, Mailbox, and Hub Transport. In order to utilize the new High Availability features built into Exchange 2010, it appears we need to deploy a third server, dedicated to CAS. Three questions: first, is it correct we need a third server running a dedicated CAS role in order to achieve HA in Exch 2010? Second, will it be straightforward to add this third CAS box, and third are there any good resources on doing this? Thanks!