In order to avoid some failures seen when all components of a mirror fail, it is recommended that a terminal resource (or instance or leaf node) be created. This terminal resource is a “gen app” resource that is used to tie all of the components (legs) of a mirror to a single point. This terminal instance is useful for several reasons.
- It provides a single point to take the full hierarchy out of service rather than having to select each component directly.
- It avoids some confusing transient situations where part of the hierarchy is active on one node and part is active on another node. This is especially seen while a hierarchy is being moved from one server to another. When the move is complete, all resources should end up on the same server, but while LifeKeeper is moving everything, it can look strange.
- It avoids some error situations where LifeKeeper is trying to quickly move resources from one system to another (all path failure), but the process of starting a resource is slow due to cluster failures. This will force LifeKeeper to take all resources out of service at the same time instead of taking one component out of service, bringing that component in service, then taking the next component out of service and then bringing it in service.
The terminal resource is created through the Create Resource Hierarchy option. This brings up the Create Resource Wizard, where you will select Generic Application from the Recovery Kit list.
For further information on creating the terminal resource, refer to the Creating a Generic Application Resource Hierarchy section of the SPS for Linux Technical Documentation at http://docs.us.sios.com/ under LifeKeeper > Administration > Administrator Tasks > Creating Resource Hierarchies > Creating a Generic Application Resource Hierarchy.