Exchange 2010’s five server roles
Exchange Server 2010 is divided into five separate but related server roles; the mailbox server, client access server (CAS), hub transport server, edge transport server and unified messaging server. It’s important for administrators to understand what they do and how they can be combined for an effective Exchange 2010 deployment.
The benefits of Exchange 2010 server roles
Having so many roles might seem to complicate Exchange, but experts note there are several advantages to a role-based architecture. First, adopting individual roles can improve security over previous versions.
“There was a larger potential attack footprint on the machine; 20 or 30 ports might be open on an Exchange box in the old days,” said Sean Evans, senior consultant at Blue Chip Consulting Group in Independence, Ohio. “By separating roles, you only need to worry about the client access server having port 443 open.”
Evans also noted that older server hardware is more likely to provide the resource requirements needed for one or more individual roles. This means organizations can avoid the capital expense of buying powerful new servers to host the entire Exchange Server system.
It’s difficult to say which server role is most important for Exchange 2010. It depends on the organization and its needs. Some experts suggest that the mailbox server role is most important since it’s at the core of any deployment.
Other experts suggest that the CAS is most important because it handles the majority of mail processing in Exchange Server 2010. This removes much of the functionality that existed in the mailbox server under previous versions of Exchange. Still, every organization is different and other admins have focused on other roles. “Unified messaging is extremely important for us,” said Joe Chiarchiaro, senior messaging engineer with Grant Thornton LLP. “We’re moving our voicemail platform to Microsoft unified messaging on [Exchange] 2010.”
Distributing Exchange 2010 server roles
Exchange Server architects have the flexibility to distribute roles across hardware platforms. A basic Exchange Server 2010 deployment involves a mailbox, client access and hub transport server on the same physical box. This is the minimum set of roles needed to store, route and deliver messages inside and outside an organization.
It is also possible to add the UM server to the same physical system; the edge transport server cannot coexist on the same computer as other server roles. The physical server must have enough resources to support all roles. This setup is often the most cost-effective approach for smaller, cost-conscious businesses. Blue Chip’s Evans also points out that licensing costs can be mitigated when configuring combined (multi-role) servers.
Distributing roles across multiple servers enables an Exchange organization to scale them according to specific needs. When performance demands increase, segregate affected role(s) on separate servers to make the most of the available computing power. You can also group servers to boost performance and resilience; migrating roles to larger and more capable boxes according to traffic loads can also help.
When selecting servers to host Exchange Server 2010 roles, experts say there are few concrete rules because system requirements aren’t spelled out. However, experts recommend referring to Microsoft best practices for hardware sizing.