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

4.5.4 Load factors
► Monitor resource use.
Check for processor, memory, and disk use before, during, and after each test
run to see if there are any unusual patterns. If the target environment is using
shared infrastructure, make sure the shared component is performing under
the projected shared load.
► Isolate network traffic as much as possible.
Using switches, there is rarely a circumstance where traffic from one server
overruns the port of another. It is possible, though, to flood ports used for
routing off the network to other networks or even the switch backbone for
heavy traffic. Make sure that your network isolates the testing environment as
much as possible prior to starting, because performance degradation of the
network can create unexpected results.
► Perform repetitive tests.
Reset the environment to a defined start state. This includes the database,
caches, and so on. Databases that use up datasets need to be reset in
particular. Make sure you have enough test data available.
The most important factors that determine how you conduct your load tests are
as follows:
► Request rate
► Concurrent users
► Usage patterns
This is not a complete list and other factors can become more important
depending on the kind of site that is being developed.
Request rate
The request rate represents the number of requests per time unit. In Web-based
environments this is mostly expressed as number of HTTP requests per second.
It is critical that the request rate is close to the real word load expectations.
Concurrent users
The concurrent users number expresses the numbers of users concurrently
requesting service from your environment at a point in time. This number of users
is really firing requests to your system at a given point of time.
110 WebSphere Application Server V7.0: Concepts, Planning, and Design