Morimoto points out that Lync in the SMB market can be rolled out with as few as two servers. The need for separate servers "depends on scale," he says. "For your minimum configuration where you're doing in-house instant messaging, Web conferencing, external IM/Web conferencing, your minimum buy is two servers. You have to have an internal server and a server on the edge. They can be virtualized. In our environment I have three servers running Lync. I have one internal server running IM/Webconf, an edge server and a voice server -- all virtualized."
If a customer runs Lync Standard Edition, "they need three servers total, two of which are optional: an edge server (optional, which is in the DMZ, and enables remote access) and the XMPP Gateway (which is optional), and Standard Edition Server (everything else)," says Microsoft.
Microsoft says that an enterprise can use a setup similar to Convergent Computing's: one or more edge servers in the DMZ (although Microsoft says this separate server is optional), back end servers (SQL databases) and front end servers (for almost all the other features or "roles" that Lync offers).
But here's the catch: With the Enterprise Edition, only some of Lync's features, called "server roles," can be colocated on the same physical servers (reference architecture is here). According to Microsoft, many specific server roles "must each be deployed on a separate computer." This includes Director, Edge Server, Trusted Application Server, Group Chat and others. Using Microsoft's reference architecture of 14 servers, Lync can support "upwards of 80,000 users," Microsoft says.
But there's another catch, too. For such large-scale deployments, Lync Enterprise Edition "requires the use of load balancers," a Microsoft spokeserpon says. "Enterprise Edition Servers are deployed in 'pools' which support up to 10,000 users per server and 80,000 users per pool." (Reference here.)
Plus, Microsoft recommends that Exchange be run on its own servers, too.
For the SMB, Microsoft says the Standard Edition supports up to 5,000 users. It also says that the Standard Edition supports failover, contrary to popular belief that it doesn't. "This is new with Lync: users fail-over from one Standard Edition Server to a second and failover does not require load balancers."
Morimoto points out that these support numbers don't tell the whole story for telephony services, either. The configuration is really dependent on how many users can be expected to be on the phone concurrently. Morimoto will confidently put 5,000 users on a single Lync Instant Messaging server and 2,000 people on a single Web conferencing server.