Clustered topologies

To maximize the high availability capabilities of IBM® InfoSphere® Information Server, install it on a file system that is shared by eight or more computers in which all tiers are implemented within clusters.

In this topology, all tiers are configured with the most advanced high availability solutions, and both application server clustering and metadata repository tier clustering are implemented. The cost in hardware is high because a minimum of eight computers are required:

  • Two computers for the engine tier, configured with the active-passive failover solution
  • Three or more computers for the services tier, configured as an IBM WebSphere® Application Server Network Deployment cluster (the WebSphere Application Server Deployment Manager and managed nodes are deployed on dedicated computers)
  • One computer for the front-end dispatcher (typically a web server) that sends requests to the IBM WebSphere Application Server Network Deployment cluster
  • Two computers for the metadata repository tier that runs on IBM Db2® high availability disaster recovery (HADR) with the Automatic Client Reroute

The following diagram illustrates a topology with a clustered application server and metadata repository tier with clustered Db2.

Figure 1. Fully clustered topology
This diagram is described in the surrounding text.

Topology dimensions and analysis

You can adapt this topology as needed to meet available resources and specific requirements. For example, to reduce hardware cost, you can consolidate some of the tiers and components on fewer computers. You can also collocate some of the services tier cluster nodes with the Db2 HADR instances of the metadata repository tier or collocate the front-end web server with one of the Services tier nodes. Similarly, if performance and scalability at the services tier is more important than high availability, then you might consider configuring the metadata repository tier with the active-passive failover solution rather than with the Db2 HADR technology. Additionally, the engine tier and metadata repository tier can be consolidated on the same computers to mitigate the cost of two additional computers.

Table 1. Scenario analysis: Fully clustered topology
Consideration Advantages and disadvantages
Level of high availability
  • The failure of a node in the WebSphere Application Server cluster does not cause service interruption. However, a slight degradation of performance might occur.
  • The failure of a node in the metadata repository tier cluster causes minimal or no service interruption.
  • The failure of a node in the engine tier causes up to a 10-minute interruption in engine operation, while failover occurs and the other node takes over. However, activities that do not require the engine tier continue without interruption.
  • The topology is highly scalable.
  • The topology supports many concurrent users.
  • You can add nodes to the WebSphere Application Server cluster to improve the performance and throughput of the application server.
  • For metadata repository configurations within an Oracle Real Application Clusters (RAC) cluster, add nodes to improve the performance and throughput of the metadata repository.
  • To increase engine performance, add additional parallel engines.
  • The topology requires a complex security setup that includes multiple firewalls and other security considerations.
  • If the security of one node or tier is compromised, the entire system is not necessarily compromised.
  • The topology is highly complex.
  • You must understand WebSphere Application Server clustering.
  • You must understand IBM Db2 clusters if you are using clustered or HADR Db2.
  • You must understand Oracle RAC clusters if you are using Oracle RAC.
  • The topology might require the implementation of high-availability cluster-management software, which might be difficult to implement.
  • The maintenance of this topology is complex.
  • The topology is highly flexible because you can take a server offline for maintenance, and the rest of the system remains operational.
  • The isolation of each tier on one or more separate computers enables groups of users within the organization to be responsible for or use particular tiers.
Cost The cost is high.