You can combine servers of different types to make a system, although only one storage role can exist in a system. This server may be a dedicated storage server or a single server with both the storage and application roles combined with or without additional dedicated application servers. The system therefore is versatile enough to meet different implementation needs of customers from a single box solution for a small office to front-end/back-end topologies, where the front end performs the application role and the back end performs the storage role. You can design your system so that the location of the front-end application servers is remote from the back-end storage server. This flexibility allows you choose either distributed or centralized system topologies for your organization.
When your system requires more than one server, Avaya recommends that one of the servers be a dedicated storage server. You can use an Avaya message store server or a third-party message storage server. When you use a third-party storage server, you still need the Avaya message store server that acts as the AxC/Directory server. The AxC/Directory server is used for notification capabilities, the LDAP database, and to provide communications between the application servers and the third-party storage server. The AxC/Directory server is also used to store user properties, name, and greeting recordings. All voice messages are stored on the user’s third-party storage server.
Messaging is designed to provide redundancy through a distributed cache mechanism in case the storage server becomes unavailable. However, this redundancy cannot be fully achieved if part of that cache is also on the storage server.