Wednesday, 06 May 2015 00:00

Exchange Server 2016 Architecture, farewell to CAS role

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The Exchange Server 2016 built on the similar architecture as in Exchange Server 2013, with one major change by removing the Client Access Server role. MS has removed Client Access Server role and introduced client access services to the Mailbox role. As a result, the Mailbox server role contains,

1. The logic to route protocol requests to the correct destination endpoint
2. Hosts all of the components and/or protocols that process, render and store the data.

It might remind some of us the architecture in Exchange Server 2003, but with a FE role. However, we still need to wait and see the actual product and its capabilities.

As per the introductory note, it is underlining that MS is not compromising the backend infrastructure client connectivity security. Even by removing the CAS role, no clients would connect directly to the back-end endpoints on the Mailbox server; instead, clients connect client access services and are routed (via local or remote proxy) to the Mailbox server that hosts the active database that contains the user’s mailbox.

There are changes in the architecture of DAG as well. As usual, the building block concept is still valid, as the additional mailbox servers can be added to form HA unit with the following additional enhancements,

1. DatabaseAvailabilityGroupIpAddresses is no longer required when creating a DAG. By default, the failover cluster will be created without an administrative access point, as this is the recommended best practice.
2. Replay Lag Manager is enabled by default.
3. Lagged database copy play down can be delayed based on disk latency, thereby ensuring active users are not impacted.
4. Database failovers times are reduced by 33% when compared to Exchange Server 2013.

The following diagram from MS shows the client protocol connectivity.

PA-Client Protocol Connectivity

This is not all, there are major other developments in the overall architecture, please follow the article from Microsoft Exchange Blog here. Happy reading.



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