The virtualized UM server must be running as the guest operating system under Windows Server 2008 R2 Hyper-V. Windows Server 2008 R2 Hyper-V is a powerful virtualization technology that lets organizations take advantage of the benefits of virtualization without having to buy third-party software. By deploying Exchange 2010 together with Windows Server 2008 R2 Hyper-V technology, an organization of any size can avoid the complications that can arise from dealing with third-party virtualization software vendors.

An Exchange 2010 SP1 server that is running the UM server role must be the only Exchange role within a single virtualized server or Hyper-V environment. Other Exchange 2010 server roles, such as Client Access, Edge Transport, Hub Transport, and Mailbox, are not supported in the same virtualized server as the UM server role.

We recommend that the computer that is running the virtualized UM server have at least four CPU cores, and at least 16 GB of memory. For virtualizing UM, the essential requirement is a 1-to-1 mapping of physical cores to virtual cores, and no overbooking. We recommend that the virtualized UM be configured to use at least 2 GB of RAM per core.

In this configuration, a virtualized UM server that experiences a typical mixture of user and caller interactions can handle fewer concurrent calls than a physical UM server that has the same specifications. Under a sustained load, tests show that a virtualized UM server that is configured as described can handle 40 concurrent calls if Voice Mail Preview is active for all UM users, and it can handle 65 concurrent calls if Voice Mail Preview is not in use.

UM does some media (audio) I/O and processing. For the production and consumption of this media, the UM role must be able to keep up with the demands of other endpoints or the user experience will suffer. For example, users may notice audio dropout, either directly for playback or indirectly if speech recognition accuracy is affected.

Facts to consider before deploying UM in a virtualized environment

The Exchange 2010 UM role provides voice mail services, and consolidates voice mail and email messages into a user’s Inbox. For more information about the UM server role, see Voicemail with Unified Messaging in Exchange 2010.

An organization might have many different reasons to want to virtualize an Exchange environment. The most common reasons for most organizations are as follows:

• To consolidate underused Exchange servers onto one physical server for increased hardware utilization.
  
  
• To consolidate Exchange Client Access server (CAS) and HUB server roles into a virtualized environment together with other server roles on the same or different physical servers (especially useful for small and medium-sized organizations or for branch offices of large organizations).
  
  
• To save space, power, and cooling for the servers that are running Exchange.
  
  

Exchange can be virtualized on one or more servers. A small organization can have a single server that provides all the required Exchange roles and functionality. A large organization requires a more complex configuration in which the Exchange roles are installed on multiple servers for the CAS, Hub Transport, Edge, Mailbox, and UM roles. Each of these roles includes its own unique workload characteristics. Typically, the different server roles work most intensively with the following components:

• Mailbox: processor, memory, disk
  
  
• CAS: processor, memory
  
  
• Hub Transport: memory, disk
  
  
• UM: processor, disk
  
  

You must perform careful planning and workload balancing for all of the server roles to determine the optimum configurations. All server roles can be expanded to additional servers to provide high availability and failover for your Exchange environment.