A common question administrators ask themselves during the Microsoft Lync 2013 design process is "How will our hardware specifications stack up to expected user usage?" The same question has been common for previous editions of Lync, all the way back to Live Communications Server (LCS) 2005. Designing a Lync environment has become more complex, and admins need to have accurate predictions when it comes to utilization of server resources. They need to know how many users will leverage particular features, such as IM, conferencing, or Enterprise Voice, so that they can appropriately size and forecast the hardware and quantity of server roles they'll need to implement.

To help with this increasingly important process, Microsoft recently released the Lync Server 2013 Capacity Calculator, which is a free tool you can download from the Microsoft Download Center. You might be familiar with the similar tool Microsoft provided for Lync 2010. Let's take a look at this new version and what it can do for your Lync planning efforts.

Related: The Lync Server 2013 Planning Tool

Using the Capacity Calculator

The Lync 2013 Capacity Calculator is a spreadsheet-driven tool that lets you input a series of numbers that are relevant to your planned deployment and expected user workload. After you enter the numbers, Microsoft Excel performs a series of calculations and displays a view of the expected CPU, memory, and bandwidth usage. The Lync 2013 calculator covers the following four areas:

  • IM and presence
  • Enterprise Voice
  • Audio and video conferencing
  • Mobility

For each of the four areas, you enter your information into the white and orange cells; the orange cells start with a default value, which you should update to match your environment. The yellow cells contain calculations based on the entered values in the white and orange cells.

IM and presence. In this section, you enter the number of Lync 2013 users that you expect to be concurrently signed in for IM/presence. The option for configuring the number of contacts in a user's contact list is hard set to 80 and not configurable. As Figure 1 shows, the yellow output columns show the percentage of CPU usage if the entire user load were handled by a single Front End Server.

Lync Server 2013 Capacity Calculator IM and presence table

Enterprise Voice. Enterprise Voice is Microsoft's software-powered VoIP solution for leveraging Lync 2013 to make or receives calls to a Public Switched Telephone Network (PSTN). In the spreadsheet, you enter the number of users that you expect to enable for Enterprise Voice in the organization. As Figure 2 shows, the output cells depict a breakdown of Enterprise Voice users in different scenarios and percentage of CPU usage if the entire user load were handled by a single Front End Server.

Lync Server 2013 Capacity Calculator Enterprise Voice table

Conferencing. Lync conferencing lets users participate in real-time audio or video conferences without the need for external services. For this section, you enter an approximate percentage of users that are in Lync 2013 conferences at any given point in time during working hours as well as a few other variables. Figure 3 shows the outcome with a breakdown of conferencing scenarios and percentage of CPU usage if the entire user load were handled by a single Front End Server.

Lync Server 2013 Capacity Calculator conferencing table

Mobility. Mobility features provide Lync Server 2013 with functionality on mobile devices. You need to enter the percentage of users in your organization that are enabled for mobility. The calculated results depict the percentage of CPU usage if the entire user load of mobility users were handled by a single Front End Server, as Figure 4 shows.

Lync Server 2013 Capacity Calculator mobility table

Putting It All Together

In the end, what you have is a spreadsheet that shows the results of all four workloads. The Recommendations section gives you the total server count for Front End, Edge, Archiving, and Back End (SQL Server) servers needed for your environment, as Figure 5 shows.

Complete view of the Lync 2013 Capacity Calculator

Now that we have all this information, what can we do with it? The Lync Server 2013 Capacity Calculator gives you a rough estimate of the hardware requirements and server count based on the information you entered to suit your environment's needs. A nice feature of the capacity spreadsheet is that even after you have the final calculations from the spreadsheet, you can edit the final server count (specifically the Front End server) to see how the average CPU percentage is affected per server, along with the network Mbps and the memory configurations. This trick gives you a quick way of seeing what could happen if you deploy your environment with more -- or fewer -- servers than the tool recommends.

Learn More: What's New in Lync Server 2013