Cluster considerations

To increase capacity and availability, multiple portal servers can be clustered with IBM® WebSphere® Application Server Network Deployment. In a cluster, the portals share a common configuration and the load is distributed evenly across all cluster instances.

HCL Digital Experience comes standard with WebSphere Application Server Network Deployment, a distribution of IBM WebSphere Application Server that provides a Deployment Manager server type for centrally managing and clustering a series of servers. To cluster a series of portal servers means that all portal instances share configuration, including database, applications, and portlets, and site design. The cluster provides a domain against which most administrative actions are done once and synchronized with each server in the cluster. This action both simplify administration and ensure that all cluster members are configured and behave identically.

A server cluster also provides a shared domain in which session and cache data can be replicated and kept consistent across all members of the cluster. The cluster also provides an application synchronization mechanism that ensures consistent application management (start, stop, updates, and so on) across the cluster.

WebSphere Application Server provides an HTTP Server plug-in that can balance user traffic across all members of the cluster. And through a feature called "session affinity", ensure that a user remains bound to a specific cluster instance during their session to improve efficiency and performance. Additionally, in the event a cluster member is down the workload management features of the plug-in recognizes that the instance is no longer available and route traffic around it.

There are two types of clusters: vertical and horizontal clusters. Most large-scale deployments are mixtures of both cluster types.

It is also possible to deploy multiple portal clusters to improve availability, failover, and disaster recovery.

It is recommended that you review the cluster guidelines and limitations topics for more information about what is involved in setting up a cluster.

Restriction: The serverName is hardcoded to HCL Digital Experience. The serverName cannot be changed in a stand-alone environment. If you do change it, the ConfigEngine scripts do not work. For a clustered environment, see Technote 1370392 for options on replacing the HCL Digital Experience JVM.