WebSphere Application Server V7.0: Concepts ... - IBM Redbooks

Advantages
Disadvantages
Sample topology
This topology is designed to maximize scalability, workload management, and
high availability. It has the following advantages:
► Single points of failure are eliminated for many components (Web server,
application server, and so on) through the redundancy of those components.
► It provides both hardware and software failure isolation. Hardware and
software upgrades can be handled during off-peak hours.
► Horizontal scaling is done by using both the Load Balancer IP sprayer (for the
Web server nodes) and the application server cluster to maximize availability.
► Application performance is improved by using several techniques:
– Hosting application servers on multiple physical machines to boost the
available processing power
– Using clusters to scale application servers vertically, which makes more
efficient use of the resources of each machine
► Applications with this topology can make use of workload management
techniques. In this example, workload management is performed as follows:
– The Network Dispatcher component of the Load Balancer to distribute
client HTTP requests to each Web server
– WebSphere Application Server workload management to distribute work
among clustered application servers
The topology has the following disadvantages:
► This appendix is an example of a standard implementation, but it should also
be noted that it is one of the most complex. Consider the costs of
administration and configuration work in relation to the benefits of increased
performance, higher throughput, and greater reliability.
► Isolating multiple components and providing hardware backups means that
more licenses and machines are needed, increasing the overall cost.
This section addresses a simplified subset of the topology described in the
previous section. Figure A-2 on page 505 shows the sample topology that we will
implement.
504 WebSphere Application Server V7.0: Concepts, Planning, and Design