Differences Between OCS 2007 R2 and Lync 2010
Lync 2010 introduces a new infrastructure requirement from OCS 2007 and OCS 2007 R2. The new feature such as communicate server sites, separation of AV conferencing role from the front end role, the modification to director role and integration of mediation server did not exist in previous version of OCS 2007. The communications server site is very similar to AD-site which defines as set of well-connected computers such as LAN. Each of the sites must be a central hub site or a spoke branch site. Hub site must contain a least one Front-end server or a pool. Spoke site/branch will contain a survivable branch appliance when deploying enterprise voice.
Lync 2010 Server Draining Feature
Lync 2010 has a feature that allows high availability by allowing administrators to stop taking new connections on a front-end server that is part of a pool. Of course, this allows server to serve existing connections while rejecting others. This feature is very similar to Exchange 2010 maintenance mode. Also, many windows administrator are familiar with NLB, which has the draining feature. When existing connections are ended, the system can be taken down for maintenance.
Lync 2010 allows AV conferencing role to be offloaded from the Front-End server, which wasn’t a feature in the previous versions. This means AV conferencing role can be installed by itself. By allowing this, Lync infrastructure will become a lot more scalable compare to OCS 2007. The director role is now also allowed to be offloaded as a single role. Back in OCS 2007, it requires the server to run a full blown SQL in the backend, which is not the case in Lync 2010.