Providing Open Architecture High Availability Solutions

4.3.2 Application Environment

The HA framework defines an operating environment for the application. Different applications

will have different needs and expectations of the operating environment, which include:

• Non-HA aware (active/spare) — these applications are written without any special coding to

take advantage of the HA framework features. These applications must be cold restarted after

a failure has occurred.

• Active/Standby mode — these applications need to have some knowledge of the HA state of

the system. They may do some sort of data replication and checkpointing to improve the

recovery time. The standby application expects notification from the HA middleware when it

must change state (e.g., standby to active). Other HA events may also be used for

communication path changes, storage changes, etc.

• Active/Active mode — these applications always handle live traffic, but change the extent of

their active domain depending on the state of the system. The HA middleware must notify the

application of the relevant cluster events, so that it can take the necessary internal

reconfiguration steps.

Figure 11. Application HA Models

Active/Spare

Active/Standby

Active/Active