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

Advantages
Implementing vertical scaling in your topology provides the following advantages:
► Optimized resource use
With vertical scaling, each application server running its own JVM uses a
portion of the machine’s processor and memory. The number of application
servers on a system can be increased or decreased to optimize the resource
use of the machine.
► Growth beyond the limits of a single JVM
A vertical scaling implementation allows you to grow with your implementation
beyond the limits of a single JVM as you can run multiple JVMs in parallel.
► Benefits from WebSphere Application Server workload management
capabilities
As vertical scaling is implemented through clusters, it allows you to benefit
from WebSphere Application Server workload management.
► Failover support
Due to the fact that vertical scaling is implemented using clusters, vertical
scaling topologies can also take advantage of the failover support provided by
WebSphere Application Server. If one of the application server processes is
stopped, the remaining cluster members will continue to process and realign
the workload.
Disadvantages
If you are using vertical scaling, there are some limitations and possible
drawbacks to consider:
► Single points of failure
Unless you combine the vertical scaling architecture with horizontal scaling,
you still have single points of failure (like hardware, operating system
processes and so on) in your architecture .
► Additional overhead
To implement vertical scaling you need WebSphere Application Server
Network Deployment. You need additional application server processes like
the deployment manager and the node agent process to manage such an
environment.
► Additional planning and implementation work required
To benefit from the load balancing and failover capabilities, you need to plan
for these scenarios. For example, to benefit from failover mechanism, you
need to think about what is required for a successful failover (like session data
and so forth) and size for all possible situations carefully.
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