With the Lync Server 2010 RC available, the details of what it will take to run Lync in production are emerging. One really nice change from OCS 2007 is that Lync is now fully supported when virtualised. With OCS 2007, only some roles were supported, although anecdotal evidence suggested OCS would work OK virtualised – the issue was more with the client.
This means that all major workloads, including presence, IM, conferencing and Enterprise Voice can be run in a virtual environment. This includes Standard and Enterprise editions. There are some restrictions on virtualisation platforms though, only VMware and Hyper-V are supported. For both virtualisation platforms, only Serve 2008 R2 is supported. And for Hyper-V, you must also run the host as Server 2008 R2. Microsoft will support virtualisations using SE to support up to around 2000 users and Enterprise Edition pools supporting up to 40k users. Edge servers can also be virtualised.
For Hype-V at least, the hosting requirements will significant: 8 Core 2.27Ghz processors with 16GB+ of ram and fast disks (particularly for your back end SQL servers). With virtualisation, your overall consolidation ratio is around 3:1 A suitably speced out host machine will support around 4 Front End servers, or 4 A/V Conferencing Servers for a user base of up to 40k users. For full functionality, you’d also want at least Directors (2 Director roles can be co-located on a single Hyper-V host) and two Edge servers (also co-located on a single VM host). You can also co-locate your Monitoring and Archiving server roles.
You can also virtualise your SQL Server back end database, but in a large Enterprise environment, you may just want to keep your back end cluster as a pair of real servers. You can of course, co-locate two SQL Server VMs on a single host to serve as your fail over back end cluster. Although this only provides resilience in the case the guest OS or applications go down!
The total level of consolidation in such a scenairo would be from around 19 servers, down to around 6 or 7 large hosts machines. You’d then need to consider your Mediation Server requirements! To some degree, the number of mediation servers required will be based on your requirements (how many PSTN ingress/egress locations do you have and what sort of gateways are you using). With Lync 2010’s Media Bypass facilities (and suitable PSTN gateways!) you could co-locate up to around 4 Mediation Servers on a single host. My guess, although I do not have the means to test it) is that you could probably support more Mediation Servers on a given host, depending on the Gateway architecture