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7.1.3.8: Multiple WebSphere domains sample topology

7.1.3.8: Multiple WebSphere domains sample topology

Overview

The following figure shows an example of how an application can be implemented over multiple WebSphere Application Server administrative domains.

multidomtop.gif (15562 bytes)

The example application runs simultaneously in two administrative domains, each hosted on a different physical machine (Machines A and B). Network Dispatcher is used to distribute incoming HTTP requests among the two domains, presenting a single image of the application to clients. A backup Network Dispatcher node provides failover support.

In this example, the application server clones in both domains are created from the same model so that identical versions of the application run in each domain. However, you can run a different version of the application in each domain. Because the domains are isolated from one another, you can also run different versions of the WebSphere Application Server software in each domain.

In this example, both domains share a common application database. However, each domain is administered independently and maintains a separate administrative repository.

Typical use

Topologies that incorporate more than one administrative domain have the following advantages:

  • Isolation of hardware failure. If one domain goes offline due to hardware problems, the others can still process client requests.
  • Isolation of software failure. Running an application in two or more domains isolates any problems that occur within a domain, while the other domains continue to handle client requests. This can be helpful in a variety of situations:
    • When rolling out a new application or a revision of an existing application. The new application or revision can be brought online in one domain and tested in a live situation while the other domains continue to handle client requests.
    • When deploying a new version of the WebSphere Application Server software. The new version can be brought into production and tested in a live situation without interrupting service.
    • When applying fixes or patches to the WebSphere Application Server software. Each domain can be taken offline and upgraded without interrupting the application.

    If an unforeseen problem occurs with the new software, using multiple domains can prevent an outage to an entire site. A rollback to a previous software version can also be accomplished more quickly. Hardware and software upgrades can be handled on a domain-by-domain basis during offpeak hours.

  • Improved performance. Running an application using multiple smaller domains can provide better performance than a single large domain because there is less interprocess communication in a smaller domain.

Using multiple domains has several drawbacks:

  • Deployment is more complicated than for 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 because each domain is administered independently. This problem can be reduced by using wscp and XMLConfig scripts to standardize and automate common administrative tasks.
  • Using multiple administration repositories (databases) makes performing backups more complicated.
Go to previous article: Demilitarized Zone (DMZ) sample topology Go to next article: Multiple applications within a node sample topology

 

 
Go to previous article: Demilitarized Zone (DMZ) sample topology Go to next article: Multiple applications within a node sample topology