8.2.1 Isolation

LPARs are natural homes for WebSphere nodes. A single physical server can host many nodes, with the added advantage that each node is a separate installation of the operating system and is isolated from the others. This has a significant impact on the ability of the system to be able to provide different levels of service to different applications with differing non-functional requirements.

For example, if one application has a requirement that it must respond to requests within (say) two seconds, and another application does not have such a requirement, it makes sense that in a heavy load situation, the application with no specific requirement is not allowed to take resources away from the one with a two-second requirement. By simply placing them on separate LPARs and setting hard limits on the maximum amount of resources available to the relevant partition, it is possible to arrange it so that the two-second rule cannot be degraded by the consumption of the application without such a requirement.

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