Lync Server Enterprise Edition

The Enterprise Edition of Lync Server provides a scalability jump compared to Standard Edition, and provides additional high-availability options. The increase in scalability results from the separating of roles onto separate systems for better performance, and also the use of more robust components in certain areas. For example, whereas Standard Edition can use only a local SQL Express database, Enterprise Edition requires the use of a full SQL instance installed on a dedicated system. In this one area alone, scalability is improved not only by using a more robust database, but also by isolating the database load from other systems.

In terms of high availability, Enterprise Edition provides several advantages compared to Standard Edition. Although the Front End Pool Pairing feature is available with either edition, only Enterprise Edition allows for the failure of a Front End server with no resulting loss of functionality for the pool users. This is possible because Enterprise Edition allows the installation of separate Front End servers for the same pool within a particular site. An additional resiliency advantage is that Enterprise Edition requires a separate database for backend data storage, which presents the opportunity to leverage native SQL high availability for the Lync data. Lync Server 2013 supports SQL mirroring, which requires two backend SQL servers and uses data synchronization between the two systems.

Of course, the additional scalability and high availability provided by Enterprise Edition come at a higher cost, in terms of both additional systems and licensing. A typical Enterprise Edition deployment at a given site consists of at least two Front End servers (up to a maximum of 10 per pool), with hardware load balancers (or a combination of hardware load balancers and DNS load balancing) used to distribute the load between the systems. At least one SQL server system would be used to store the backend data, although two such systems with SQL mirroring would be recommended for redundancy. On the Front End systems, several other Lync server roles can be collocated, including Mediation Server, Monitoring Server, and Archiving Server. The Mediation Server role can also be installed separately from the Front End to increase performance. Other systems that can be added to provide increased functionality with an Enterprise Edition deployment include one or more PSTN gateways to enable Enterprise Voice features, Persistent Chat Server, and an Edge Server or Edge Server pool to support external connectivity.