One of the toughest challenges with any server deployment is accurately estimating the capacity of a certain server to service users. Some products provide very specific services that can be accurately calculated, but UAG, unfortunately, is not one of those products. The impact of each user on the server is incredibly varied, depending on the published application and what type of resources it uses, the UAG services in use (SSL, SSTP, NC, DA, applications, ActiveSync, RPC-over-HTTP proxy, and so on) and the way they are used by the users. Basically, the only way to know a specific server's abilities is to measure how it reacts to activity over time. An essential tool for this is the Performance Monitor (a.k.a. PerfMon), which is built into all versions of Windows.
By recording performance over time, analysis can be done, showing the relationship between the quantity of users who use the server and its ability to service their requests. The Performance Monitor...