There are many possible system architectures as to how MES modules are installed and how they interact with other key systems. Most users begin using a standard architecture, where MES and all components are all installed on a single machine. As your system expands, you can investigate into other possible architectures.
If you have multiple production sites to meet MES functionality and if you also want to collect data in a central location such as the headquarters, you must go with an enterprise architecture.
In the architecture shown below, you can see a data center and three production sites. The production data from each sites is to be stored in the data center. The production sites must run independently from each other and have to run even when the communication with the center site goes down. So in this situation it is really important that all the production sites have an Ignition server by themselves.