It is possible to migrate from a Cisco Unity Voicemail Only configuration to a Cisco Unified Messaging configuration. It can be a single Cisco Unity Voicemail or a Cisco Unity with failover configuration. In order to migrate, complete the steps in these documents based on the requirements:
The same methods can be used in order to change the configuration for a Cisco Unity 4.x system. Make sure Cisco Unity, Microsoft Exchange and DC/GC are different server platforms. Exchange and DC/GC can be on the same platform.
In order to add a pair of Cisco Unity failover servers, Microsoft SQL Server 2000 must be installed on the primary and secondary servers. The Microsoft SQL Server Desktop Engine (MSDE) 2000 is not supported on either server with Cisco Unity failover.
Note: It is not possible to configure the Cisco CallManager Express located in a remote site with Cisco Unity failover. Instead, it is possible to integrate Cisco Unity Express with each Cisco CallManager Express.