Configuration data

Now that we have covered how deployments work (push and pull) in DSC and covered the workflow (authoring, staging, and execution) for using DSC, we will pause here for a moment to discuss the differences between configuration files and configuration data.

It is important to understand the concept of the separation of the what from the where that we covered in Chapter 1, Introducing PowerShell DSC, when considering how to deploy servers, applications, and environments using DSC.

The DSC configuration blocks contain the entirety of the expected state of the target node. The DSL syntax used to describe the state is expressed in one configuration file in almost a grocery list format. It expresses all configuration points of the target system and is able to express dependencies between configuration points.

DSC configuration data is separated from DSC configuration files to reduce variance and duplication. Some points that are considered data are software version numbers, file path locations, registry setting values, and domain-specific information, such as server roles or department names.

You may be thinking what the difference between the data you put in a configuration file and a configuration data file is. The data we put in a configuration file is structural data, data that does not change based on the environment. The data we put in configuration data files is environmental. For example, no matter the environment, a server needs IIS installed in order to serve web pages. The location of the source files for the web page may change depending on whether the environment is the development environment or the production environment. If you are wondering where these files reside and when you use them, we will cover each of them in term in the coming chapters.

The structural information (that we need IIS for) is contained in the DSC configuration file and the environmental information (source file locations) is stored in the configuration data file.

Configuration data can be expressed in DSC in several ways. Let's look at each of the ways in detail.