User Guide

Issues Affecting Successful Scalability Implementations 233
• Minimize distributed environment load testing
Load testing in a distributed environment can be problematic if the network on
which you are performing your load tests becomes congested, resulting in poor
response times. Additionally, if everyone else in the organization is using that
network for their everyday activities, such as e-mail, source control, and file
management, an increased load going over the network will likely cause
significant network degradation for them. As they likely have nothing to do with
the testing effort, this situation can cause great frustration.
In such a scenario, it may be more effective to physically sit in front of the server
on which the application resides and perform the tests locally rather than bring
the entire LAN or WAN to a slow crawl. Also, by testing locally, you are better able
to rule out the network as the source of the scalability problems. Alternatively,
you may be able to configure a separate subnet on the LAN or WAN that is
distinct from the subnet on which everybody else in your environment uses
network services.
You should now have a good overview of what scalability implies, the core elements
that comprise it, some of the issues that affect successful implementations, and the
tasks that must be performed to verify that your Web applications are able to achieve
satisfactory scalability.
The next section describes Web site availability and reliability concepts and
considerations.