Topology Configurations for Multi-Cell Routing
In a multi-cell situation IBM recommends using either the star or the peer-cell topologies.
Neither of these topologies employ core-group bridges to link cells. For WAS V7.x and higher, core-bridge topologies are discouraged.
Star Topology
The Star Topology works well if we have multiple cells and the center cell contains all on demand routers. We remove all ODRs from the point cells and move them into the center cell. For the sake of high availability it's a good idea to cluster the ODRs, and to keep them on separate hardware and separate power supplies, etc. We would then use the linkCells script to link the cells. A star topology is highly-scalable, as we can add more cells as necessary. Discovery is also still there -- if we add applications to one cell or another, the ODR will learn of them automatically, just as if everything were in one cell.
Indications for the star topology include:
- Consolidation of ODRs in a single center cell can route to application servers in multiple point cells.
- Multiple cells share the same hardware resources. A single Application Placement Controller (APC) in the center cell can manage the performance of all cells in the star topology by starting and stopping application servers in point cells to meet current demand.
- For scalability, if a single cell is preferred from a management perspective, there are scalability limitations associated with a single cell. This multi-cell topology enables us to scale higher while still managing a single cell of ODRs, and at the same time, also managing dynamic clusters across all cells as a unit.
Peer-Cell Topology
The Peer-cell Topology works well if we have two or more disjoint data centers, one cell per data center, and we want failover capability between them. In this topology, the ODRs remain in the cells; however, the two cells are not joined via core-group bridges. In front of our two cells, we have one or more load-balancers, plugins, or sprayers which are able to both preserve session affinity (as applicable), as well as equitably distribute traffic.
Indications for the peer-cell topology include:
- The cells are peers (e.g. duplicates of one another)
- You want to join two or more disjoint data centers
- The cells we want to join do not share hardware
- The cells we want to join all need to contain ODRs
Related:
Overview of request flow prioritization Configure multi-cell performance management: Star Topology Configure multi-cell performance management: Peer-Cell Topology Create ODRs Create and configure ODRs Set up Intelligent Management for dynamic operations