Exchange wiki page includes links to Microsoft and community articles/documents/papers, that explains what Exchange 2010 Client Access arrays (CAS arrays) are all about and how you configure them according to best practice recommendations. In addition, it
provides links to white papers from vendors that offer hardware-based or virtual load balancer solutions that can be used to load balance Exchange 2010 CAS array sessions.
This page lists the Server Hardware Load Balancer (HLB) partners that has completed interoperability qualification testing with Exchange
Server 2010 and contains pointers to accompanying deployment white papers hosted by the partner (links to partner and non-partner white papers can also be found under the vendor section in the bottom of this wiki page).