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Designers working with Microsoft (News - Alert) Exchange usually set out to adhere to a series of so-called best practices in an effort to use methods that have been proven to work better than others. In the case of Exchange, CAS (Client Access Server) arrays outline a method to group a set of CAS servers together in such a way that allows them to be addressed as a single entity, according to IT expert Tony Redmond.

“Introduced with Exchange 2010, CAS arrays provided a method to group a set of CAS servers together in such a way that they could be addressed as a single entity (and had a single IP address and FQDN),” Redmond explained in a recent blog post. “Individual servers could join and leave the array over time and the array would keep functioning as long as a single server was active. All-in-all, it was a nice concept, even if a CAS array didn’t perform any load-balancing of incoming client connections.”

With Exchange 2010, best practices dictated that you should always create a CAS array within a site and assign the CAS array object to the RpcClientAccessServer property of mailbox databases.

However, with Exchange 2013, the CAS is a bit different – and as Redmond asserted, “a best practice that only arose in Exchange 2010 is consigned to the great byte wastebasket.”

“The Exchange 2013 version of the CAS is a much simpler beast as it is purely an authentication (are you authorized to connect to Exchange?) and proxy/redirect (where do you need to go to find your mailbox?) server,” he said. “No processing is performed of mailbox data by the CAS; all it does is to send on client requests to connect to the mailbox server that hosts the currently active copy of their mailboxes via HTTPS (no MAPI RPCs).”

Once the migration to Exchange 2013 is complete, the best practice of deploying CAS arrays for Exchange 2010 are pretty much dead and buried by the new developments, Redmond said.

It has been pointed out that Exchange 2013 is the result of almost 20 years of evolution and in many ways it shows: Microsoft has done an excellent job of whittling away the old while introducing the new. However, for each change that is accepted as a success – Data Loss Prevention has been implemented to stop sensitive information from being shared accidentally – others receive scorn, like doing away with context-sensitive menus in the Exchange Administration Center for Exchange 2013, TMCnet reported.

However, one brand new feature in Exchange 2013, “modern public folders,” is receiving praise – and for good reason. The new feature ultimately does away with the separate public folder database, instead integrating everything under mailbox databases in the Database Availability Group.

The old public folder replication model may have seemed like a killer feature when it debuted with Exchange 4.0 in 1996, but it hasn’t really stood the test of time.

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