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

Advantages
This topology provides the following advantages:
► Provides all the advantages defined in 5.3.5, “Topology with redundancy of
multiple components” on page 160
► Allows you to react quickly to cell level problems
► Allows stepwise WebSphere upgrades
This topology allows independent releases of WebSphere Application Server
software in each cell. Therefore, each cell can up upgraded on its own. This
lowers the risk of an upgrade and provides a fall-back scenario in case of
upgrade problems.
► Allows stepwise application upgrades
Using this topology allows independent application releases in each cell and
provides a quick fall back scenario in case you determine application
problems in your production environment 2 .
► Possible approach for disaster recovery
If the cells are located in different data centers, it is a possible approach for a
disaster recovery solution from a WebSphere perspective.
Note: The topology illustrated in Figure 5-10 is not a complete solution for
disaster recovery. For a real disaster recovery solution implementation
several issues need to be addressed:
► How do you route traffic to each of the cells?
► How will you handle affinity of requests?
► How will you handle session data?
► How will you handle security data?
► How will you address the data replication and consistency challenge?
► How will you handle a cell fail-over for each type of requests in your
application? Web requests, SIP requests, EJB Requests, Web services
and so forth
► Co-location of cells is possible
You can collocate the two cells on the same systems to achieve the software
release independence described before. Be aware that this limits the disaster
recovery usability.
2 Of course this requires some sort of compatibility between application software releases
170 WebSphere Application Server V7.0: Concepts, Planning, and Design