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
3.1Goals of the Host Application
Design goals that should be achieved for your application to perform successfully in a High Availability environment are:
•Serviceability
•Portability
•Redundancy
3.1.1Serviceability
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.
3.1.2Portability
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, “Division of Labor” on page 22.
3.1.3Redundancy
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
High Availability Software for the Intel® NetStructureTM ZT 4901 Technical Product Specification | 21 |
