Installation of IBM® XDMS in a clustered WebSphere® Application Server environment is the recommended deployment configuration.
You should also consider the various hardware topologies that are available, paying special attention to the scalability considerations that are described in the topic Evaluating your hardware environment.
As clusters, both the IBM XDMS and the Aggregation Proxy must be fronted with some network element that performs routing to these clusters and handles request processing. For Session Initiation Protocol (SIP) traffic, the XDMS cluster must have a highly available set of WebSphere Application Server proxies to do the request routing. This set of proxies is itself clustered and is fronted by some type of IP sprayer or load balancer.
For HTTP traffic destined for the Aggregation Proxy or the IBM XDMS, either the WebSphere Application Server Proxy or some equivalent HTTP router such as IBM HTTP Server or an IP sprayer can be used. In addition, the proxy/router fronting the Aggregation Proxy cluster must be configured to ensure affinity based on client IP or similar if retry counts on failed authentication attempts are used.
The IBM XDMS components use WebSphere Application Server clustering technology to achieve a highly available and scalable architecture. The Aggregation Proxy and the IBM XDMS are both independently scalable because they are both deployed in separate clusters.
In addition to WebSphere Application Server, both the Aggregation Proxy and the IBM XDMS provide core functionality that can enhance the scalability of the end-to-end solution. You can deploy clusters for the IBM XDMS in different combinations of domain and Application Unique ID (AUID).
The AUID supported by the system can be hosted all on the same IBM XDMS or subsets of them can be hosted on a dedicated IBM XDMS or IBM XDMS cluster. By partitioning to separate clusters, the overall scalability and supportable throughput as a whole is improved. For example, you can use a separate high-availability cluster and database for your resource-lists documents from your presence rules documents. Aggregation Proxy request forwarding and routing is used to control to which IBM XDMS requests are sent.
Using Aggregation Proxy request forwarding, you can configure different IBM XDMS instances to support or be dedicated to certain subscriber domains. This capability enables supporting multiple user space partitions when the total user population is too large for a single IBM XDMS cluster, or when there are different security requirements for different domains.
AUID partitioning can be used in conjunction with domain partitioning whereby the Aggregation Proxy first determines the subset of XDMS applications supporting the AUID and then discriminates between that subset for the domain matching the XUI of the requested user.
Remember that the clustering techniques for high-availability and scaling can also be combined with the partitioning techniques.