Defining all of the critical resources within Pacemaker is a good start. However, Pacemaker is not concerned with keeping related services operating together. It is designed to facilitate service management for any series of resources over a large array of servers. This is a recurring theme in this chapter, and one we have to overcome to fully leverage Pacemaker's abilities.
One way we can do this is by creating a group of related resources. When we do this, the group represents every member as a whole and must run on one server or another. This prevents the problems we had in the previous recipes, such as the possibility of new resources being started on the wrong node.
We'll create a group in this recipe and discuss other important caveats.
