To be highly available, an application must be managed as a resource in an application resource group. An application resource group can be configured for a failover application or a scalable application.
Application resources and application resource groups configured on the primary cluster must also be configured on the secondary cluster. Also, the data accessed by the application resource must be replicated to the secondary cluster.
This section provides guidelines for configuring the following application resource groups:
In a failover application, an application runs on one node at a time. If that node fails, the application fails over to another node in the same cluster. A resource group for a failover application must have the following characteristics:
Have an HAStoragePlus resource to enforce the failover of the device group when the application resource group is switched over or failed over
The device group is colocated with the replication resource group and the application resource group. Therefore, the failover of the application resource group enforces the failover of the device group and replication resource group. The application resource group, the replication resource group, and the device group are mastered by the same node.
Note, however, that a failover of the device group or the replication resource group does not cause a failover of the application resource group.
If the application data is globally mounted, the presence of an HAStoragePlus resource in the application resource group is not required but is advised.
If the application data is mounted locally, the presence of an HAStoragePlus resource in the application resource group is required.
Without an HAStoragePlus resource, the failover of the application resource group would not trigger the failover of the replication resource group and device group. After a failover, the application resource group, replication resource group, and device group would not be mastered by the same node.
For more information about HAStoragePlus, see the SUNW.HAStoragePlus(5) man page.
Must be online on the primary cluster and offline on the secondary cluster
The application resource group must be brought online on the secondary cluster when the secondary cluster takes over as the primary cluster.
Figure A–4 illustrates the configuration of an application resource group and a replication resource group in a failover application.
In a scalable application, an application runs on several nodes to create a single, logical service. If a node that is running a scalable application fails, failover does not occur. The application continues to run on the other nodes.
When a scalable application is managed as a resource in an application resource group, it is not necessary to collocate the application resource group with the device group. Therefore, it is not necessary to create an HAStoragePlus resource for the application resource group.
A resource group for a scalable application must have the following characteristics:
The nodes that are running the scalable application use the shared address to distribute incoming data.
Be online on the primary cluster and offline on the secondary cluster
Figure A–5 illustrates the configuration of resource groups in a scalable application.