In this four-part series, I will describe the new features in Exchange 2013. Part 1 covers the changes in server roles, Site Resilience, and High Availability.
I am really excited about some of the new Exchange 2013 features and other details like architecture changes, the new Public Folder concept, the fresh look of Outlook Web Access (OWA), the integration with Lync, SharePoint, and this list goes on.
Note: Exchange 2013 cannot coexist with Exchange 2003. If you are still on Exchange 2003, you may have to first upgrade to either Exchange 2007 or 2010 and then to Exchange 2013.
The Mailbox Server Role and the Client Access Server Role are the only two server roles in Microsoft Exchange Server 2013. The Exchange 2010 roles Hub Transport Server, Unified Messaging Server, and Edge Transport Server have been completely removed. The Hub Transport Server and the Unified Messaging Server features are shared between the Mailbox Server Role and the Client Access Server Role. The Exchange Edge Server Role has been completely discontinued in Exchange 2013, but you can continue to use the Exchange 2010 Edge Server Role.
Exchange 2013 – Mailbox and Client Access Server role installation
Mailbox Server Role
The Mailbox server hosts the mailbox database, which contains the mailboxes and the Public Folders. It also hosts some of the Hub Transport Service and Mailbox Transport Service. The Hub Transport Service is used for mail routing within the organization and to provide connectivity between the Hub Transport Service and the Frontend Transport Service. The Mailbox Transport Service is used to transport emails between the Hub Transport Service and the mailbox database.
Client Access Server role
The Client Access Server (CAS) role enables clients to connect to Exchange. The CAS first authenticates the clients and then proxies the request to the Mailbox server. The CAS provides two services: Client Access Service and Front End Transport Service. The Client Access Service provides authentication and redirection and works as a proxy to the Mailbox server. The Front End Transport Service offers protocol, connection, recipient, and sender filtering and also helps in identifying the active Mailbox server.
Site Resilience and High Availability
Exchange is a mission-critical application. Site Resilience and High Availability both improve the reliability of Exchange.
Mailbox server high availability
The Exchange 2013 Mailbox server uses the Database Availability Group (DAG) concept to provide both High Availability and Site Resilience features. In Exchange 2013, DAG received the version number 2.0. The configuration of DAG is now easier, and its stability has been improved as well. The Transactional Log Creation code has been completely rewritten. The new Exchange Managed Stores helps perform failover and failback much faster. Now, we also have many new and enhanced PowerShell cmdlets to perform various DAG operations to suit various situations.
Exchange 2013 – Data Availability Groups (DAG)
Client Access server high availability
The Client Access server provides high availability through a CAS array using a hardware load balancer or Windows Network Load Balancing (NLB). Each has its own advantages and disadvantages. Configuring a hardware load balancer in Exchange 2010 was a bit tricky, and you had to configure the server affinity. This is no longer a requirement. In Exchange 2013, we can use a Layer 4 load balancer (which works on IP addresses and ports) or a DNS load balancer for this purpose. Though the DNS load balancer is just an optional solution, it requires manual DNS settings modification during one or more CAS server failures.
In my next post, I will talk about some interesting Exchange 2013 architecture changes and related improvements.