When you create a SIOS Protection Suite resource hierarchy, you create the hierarchy initially on the primary server and extend the hierarchy to a backup server. Most resource instances can be active on only one server at a time. For such resources, SIOS Protection Suite defines a second kind of relationship called a shared equivalency that ensures that when the resource is in-service on one server, it is out-of-service on the other servers on which it is defined.
In the example below, a shared equivalency exists between each hierarchy level on a pair of servers. For example, the MSExch.0 resource exists on both servers, and there is a shared equivalency between the two instances of MSExch.0 (just as there is between the one DNS instance and the two volume instances).