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

– You will more likely have to call your EJBs out-of-process and pay a
performance penalty for that.
– The memory footprint of the environment will increase as each of the
JVMs has a basic memory footprint.
Location of the embedded messaging infrastructure
When using the WebSphere Application Server embedded messaging
infrastructure, you must decide in which application servers the messaging
service should run. Whether you run the embedded messaging service on a
separate application server and cluster or co-located on an application server
running your applications depends on your needs.
To determine what is best for your environment, consider the advantages and
disadvantages of running the embedded messaging infrastructure on a separate
set of application servers and clusters:
► Advantages
– The messaging service runs on a separate JVM and will not use Java
resources of your application server. If multiple applications and JVMs are
using the messaging service this might be more important.
– It is possible to tune each application server for its specific usage. This
includes Java heap tuning as well as Java runtime tuning.
– Application servers and clusters can be started, stopped, and restarted
independently from the availability of the messaging service without
causing a failover of the messaging service (and vice versa).
– You can deploy your messaging infrastructure to systems independently
from the other application servers and clusters. This allows you to deploy
your messaging infrastructure to, for example, systems where message
persistence can be implemented easiest.
– You will benefit from the runtime provisioning capabilities of WebSphere
Application Server V7.0.
► Disadvantages
– The number of application servers in your cell increases, resulting in a
more complex administration of the cell.
– Due to the higher number of application servers, your cell and your core
group grows. You will see longer cell startup times and more overhead
caused by high availability manager.
– Memory footprint of the environment increases due to additional servers.
– The deployment of your applications might become more complex,
especially when using mediation modules.
132 WebSphere Application Server V7.0: Concepts, Planning, and Design