Choosing A Platform - IBM BS029ML - WebSphere Portal Server Self Help Manual

The ability to queue requests in the network layer is a critical part of the WebSphere queuing
mechanism. For example, if there are more connection requests than available Web container
threads, then connections start to backlog, waiting for threads to be freed. If the maximum
number of backlog connections is reached, new connections will be refused. Increasing the
MaxConnectBacklog queue can extend the number requests queued in the network layer.
However, the full implication of increasing the MaxConnectBacklog queue should be
understood, as an increased value can effectively lead to latency problems with the
WebSphere plug-in resident in the chosen Web server not immediately detecting that an
application server has ceased operation (either through a deliberate stoppage or on the
occasion of a JVM crash). Choosing the most appropriate value is therefore dependant on the
results you wish to achieve.

2.5.4 Choosing a platform

The selection of a suitable platform has many factors that need to be taken into account. The
precedent is, however, usually set by cost and the immediate skill set of the team that will
install and administer the solution.
The following points should be carefully considered when making choices between hardware
platforms:
Cross platform benchmark comparisons should be done with caution. Hardware and
software differences between platforms may result in inappropriate comparisons.
If comparisons are made, pay special attention to clock speed, number of CPUs used, and
hardware manufacturer benchmarking data.
Take into account aspects beyond raw clock speed, including threading models, network
and disk I/O, instruction cache hit/miss ratios, memory speeds, and so on.
AIX and Solaris™ platforms both have much better scalability than non-UNIX platforms.
The Linux® version is a factor. The most recent versions have incorporated scheduler
changes that contribute to performance.
To achieve increased Linux performance, it has been found necessary to update to the
latest kernel and to reduce the number of Web Container threads.
Of course, actual performance depends on complex interrelationships among many variables,
including the underlying operating system characteristics.
It is strongly suggested that a three-tier approach is adopted for the solution. This is
regardless of the selected platform. Differentiating between the functional components of the
solution allows each server to be specifically tailored to the task in hand. For example, placing
the Web server on a separate physical machine from the application server allows each
machine to run with different OS characteristics. The same holds true for other server types,
such as the database servers.
It is also worth considering the licensing implications associated with choosing the platform,
as WebSphere Portal Server is typically licensed, at the time of writing, by user or by CPU. As
such, there is no distinction regarding the actual performance of a CPU.
Chapter 2. Architecture and planning
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