SIOS Protection Suite allows you to create relationships between resource instances.The primary relationship is a dependency. For example, one resource instance depends on another resource instance for its operation. The combination of resource instances and dependencies is the resource hierarchy.
In the example above, MSExch.0 is an Exchange resource, which has three dependencies – a DNS resource (DNS.0) and two volume resources (Vol.L and Vol.X).
The dependency relationships specified by the resource hierarchy tell SIOS Protection Suite the appropriate order for bringing resource instances in service and out-of-service. In the example resource hierarchy, SIOS Protection Suite cannot bring the MSExch.0 resource into service until it successfully brings into service the DNS and volume instances.