Resource Hierarchies - SIOS

Resource Hierarchies
SPS performs this check only once, after all comm paths go down. If the safety check detects that
the system is alive, failover is aborted. SPS does not re-initiate failover until all of the following events
happen in sequence:
1. At least one of the comm paths comes back ALIVE.
2. All comm paths again go DEAD.
3. The safety check activates and does not detect that the paired system is alive.
Resource Hierarchies
The LifeKeeper GUI enables you to create a resource hierarchy on one server and extend that
hierarchy to one or more backup servers. SPS then automatically builds the designated hierarchies
on all servers specified. SPS maintains hierarchy information in a database on each server. If you use
the command line interface, you must explicitly define the hierarchy on each server.
After you create the resource hierarchy, SPS manages the stopping and starting of the resources
within the hierarchy. The following topics provide background for hierarchy definition tasks:
• Resource States
• Hierarchy Relationships
• Shared Equivalencies
• Resource Hierarchy Information
Hierarchy Relationships
SPS 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 SPS the appropriate order for
bringing resource instances in service and out-of-service. In the example resource hierarchy, SPS
cannot bring the MSExch.0 resource into service until it successfully brings into service the DNS
and volume instances.
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