If you use Tableau Server you can create as many sites as you want. Sites play an important role in your overall content management strategy, and it helps to understand when to use separate sites.
Sites work well when content can remain completely separate during all phases, and there is little to no user overlap. A good (and common) example for using multiple sites is to create a separate site for each external client such as a consultant or vendor who needs access to certain content. Tableau Online is an example of this on a large scale.
However, in an organization, sometimes different areas to have overlap. For example, Finance, Sales, Marketing all might need data around company sales or employee details. In this case, creating separate sites for each of the above functions is not a good idea since it is not possible to share data or content between the various sites.
Content organization with separate sites
Pictured above, there are three separate sites for Marketing, Finance and HR. Data in the HR site under the HR data project, cannot be used by the Marketing or Finance sites. But, sometimes these departments need to use different sites.
With nested projects in 10.5, you can keep everything in one site and create top-level projects for each function like Finance, Sales, Marketing etc. Now the various projects can share data if they need to, and IT can still control visibility using Tableau permissions.
Same organization without sacrificing ability to share data
With nested projects, project owners and project leaders have full control over how content is organized within their area. They can create child projects, assign ownership to the appropriate individuals, and then manage their own project, and everything under it. This creates a more scalable and flexible governing structure compared to previous versions of Tableau, where a site or server admin was always needed to create a project.
In Tableau 10.5, the project owner or leader of a top-level project also has the flexibility to lock down their project tree or keep it unlocked. If they choose to lock their project, all the child projects (and content in all the projects) will derive permissions from the top-level project. Individual owners cannot change this. Only the top-level projects can be locked, but by keeping a project tree unlocked, a more flexible permissions model can be implemented.
This is the first step in a journey to improve content organization, management and governance. It will also help us make the Tableau experience simpler, more personal and easier to manage for business users.
To learn more about structuring your projects and granting access only to those who need it, see the following articles:
Use Projects to Manage Content Access
Project Permissions States and Defaults