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7.1.3.10: Putting it all together - a combined topology

7.1.3.10: Putting it all together - a combined topology

Overview

An example of a topology that combines the best elements of the other topologies discussed in this section is shown in the following figure.

combotop.gif (34761 bytes)

This topology combines elements of several different basic topologies:

  • Two WebSphere Application Server administrative domains
  • Two Network Dispatcher nodes (machine A in domain 1; machine J in domain 2)
  • Two HTTP servers for each domain (machines B and C in domain 1; machines K and L in domain 2)
  • Four application server nodes for each domain (machines D, E, F, and G in domain 1; machines M, N, O and P in domain 2)
  • The use of clones for both vertical and horizontal scaling. In the example topology, each node hosts three clones; in practice, the number of clones is limited by the computing resources of each node.
  • Two database servers for each domain (machines H and I in domain 1; machines Q and R in domain 2). These servers host mirrored copies of the application database and administrative database.

Typical use

This topology is designed to maximize thoughput, availability, and performance. It incorporates the best practices of the other topologies discussed in this section:

  • Having more than one Network Dispatcher node, HTTP server, application sever, and database server in each domain eliminates single points of failure.
  • Multiple administrative domains provide both hardware and software failure isolation, especially when upgrades of the application or the application server software are rolled out. (Hardware and software upgrades can be handled on a domain-by-domain basis during off-peak hours.)
  • Horizontal scaling is done by using both cloning and Network Dispatcher to maximize availability and eliminate single points of process and hardware failure.
  • Application performance is improved by using several techniques:
    • Hosting application servers on multiple physical machines to boost the available processing power.
    • Creating multiple smaller domains instead of one large domain. There is less interprocess communication in a smaller domain, which allows more resources to be devoted to processing client requests.
    • Using clones to vertically scale application servers on each node, which makes more efficient use of the resources of each machine.
  • Applications with this topology can make use of several workload management techniques. In this example, workload management can be done through one or more of the following:
    • Using the Advanced Application Server workload management facility to distribute work among the application server clones.
    • Using Network Dispatcher to distribute client HTTP requests to each Web server.

    For example, an application can manage workloads at the Web server level with Network Dispatcher and at the application server level with WebSphere workload managment. Using multiple workload management techniques in an application provides finer control of load balancing.

    Regardless of which workload management techniques are used in the application, administrative servers participate in workload management to provide failover support.

In this topology, only the loss of an entire domain can normally be noticed by users. If this occurs, the active HTTP sessions are lost for half of the clients. The system can still process HTTP requests although its perfomance is degraded.

The combined topology has several drawbacks:

  • Deployment is more complicated. The WebSphere Application Server software and application files must be deployed in each domain, which would not be the case for applications that run in a single administrative domain. Using a distributed file system that provides a common file mount point can make this task easier.
  • Multiple domains require more administration effort, since each domain is administered independently. This problem can be reduced by using wscp and XMLConfig scripts to standardize and automate common administrative tasks.
Go to previous article: Multiple applications within a node sample topology Go to next article: Firewalls and demilitarized zone (DMZ) configurations

 

 
Go to previous article: Multiple applications within a node sample topology Go to next article: Firewalls and demilitarized zone (DMZ) configurations