Intel ZT 4901 Host Application Software 3

High Availability Software for the Intel® NetStructureTM ZT 4901 Technical Product Specification 21

Host Application Software 3

Through thoughtful design and the use of a layered development approach, an application can be

developed that meets the implied robustness of a highly available system and also is a portable

entity. In addition to covering the details of developing an application that runs in a High

Availability environment, this chapter provides a foundation for understanding the issues that a

developer needs to be aware of when deploying in a multi-host architecture.

Design goals that should be achieved for your application to perform successfully in a High

Availability environment are:

•Serviceability

•Portability

•Redundancy

The first and probably most important attribute of an application is to maintain a constant level of

service. This ability to provide a minimum level of functionality is referred to as serviceability. The

concept of serviceability should not be restricted to performing the required functionality within

the domain of a single Host, but should be considered at a much higher level. An application is the

service or set of services that need to be performed within the domain of a platform. By domain we

are referring to the system that is providing the service. The system could be as simple as a system

master processor board, but more than likely the system will contain peripheral boards, chassis

management modules, various system sensors, and in the case of a redundant host architecture,

multiple system master boards.

Another goal is to design and implement a portable Host application. Some of the largest

investments that a provider makes are in the areas of application development and maintenance. In

order to preserve as much of the initial investment as possible, it is important to design the

application so that it is separated from specific platform components that may be enhanced or

changed. Portability can be achieved by isolating the application as much as possible from the

system management responsibilities required for High Availability. This separation of functionality

can be achieved through a combination of modular design and a layered software approach. This

topic is covered in more detail in Section 3.2, “Divisi on of Labor” on page 22.

In order to achieve a high level of serviceability within a Redundant Host environment, it is

assumed that the host application has the ability to failover to another application. This backup

application should be a mirrored copy of the original application that will likely reside on another