Specifications

Best Practices for Virtualizing and Managing Exchange 2013
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Exchange 2013 Resiliency
The backbone of business communication, messaging solutions require high availability. Exchange 2013
provides advanced capabilities to deliver a messaging solution that is always available. Moreover, the data
in mailbox databases is one of the most critical business elements of any Exchange-based organization.
These mailbox databases can be protected by configuring them for high availability and site resilience.
With a virtualized Exchange 2013 environment, administrators can combine the built-in, integrated high
availability features of Exchange 2013 with the failover clustering capabilities available at the host level to
provide higher availability.
Exchange 2013 Roles
Exchange 2013 has just two roles: Client Access Server (CAS) and Mailbox Server. Each provides a unit of
high availability and a unit of fault tolerance that are decoupled from one another. Client Access servers
make up the CAS array, while Mailbox servers comprise the database availability group (DAG). All of the
functionality of the Hub Transport and Unified Messaging roles found in Exchange 2010 now exist within
the Mailbox role.
Client Access Server Role
In Exchange 2013, clients (like Microsoft Outlook, Outlook Web App, and Exchange ActiveSync) connect to
the Client Access server for mailbox access. The Client Access server authenticates and proxies requests to
the appropriate Mailbox server. The Client Access server itself does not render data. The Client Access
server is a thin and stateless server; there is never anything queued or stored on it. The Client Access
server offers all the usual client access protocols: HTTP, POP and IMAP, UM, and SMTP.
The Client Access server provides high availability using a load balancer. This load balancer can detect
when a specific Client Access server has become unavailable and remove it from the set of servers that
handle inbound connections.
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Mailbox Server Role
Mailbox servers host the databases that contain mailbox and public folder data. The Exchange 2013
Mailbox Server role can be made highly available by configuring a Database Availability Group. The
Mailbox Server role uses the DAG concept to provide both high availability and site resilience features. In
addition, the new Information Store, known as the Managed Store, helps to perform failover much faster.
Data is replicated between DAG members using log shipping. Multiple copies of databases are supported
in the same site and across sites, as are automatic failovers or manual switchovers. Finally, up to 16 copies
of a database are supported across multiple servers.