Updating software on a cluster

When cluster services are active, the cluster software is interfacing with the system software and external components such as Cluster Aware AIX® (CAA) and Reliable Scalable Cluster Technology (RSCT). The cluster software might also be monitoring applications.

Installing or updating the software for any of these components might cause a disruption. This disruption might be interpreted as a failure by the cluster software and can trigger a failover or corrupt the cluster software.

Before you upgrade software, consider the following information:

• Assess the impact to the application and software that you are upgrading. For example, upgrading to CAA and RSCT might affect PowerHA® SystemMirror®.
• Before you update the active node, you must stop cluster services. If the update includes changes to the RSCT filesets, you must stop cluster services by using the Bring Resource Groups Offline option. Otherwise, you can stop cluster services by using the Unmanage Resource Groups option.
• To update the software, if you must restart the system, you can stop cluster services and move any resource groups to a standby node before the updates are applied.
• If you are updating AIX or PowerHA SystemMirror software, take a cluster configuration snapshot and save it in a directory outside the cluster.
• Back up the operating system and any critical data. Prepare a backout plan in case you encounter problems with the upgrade.
• Test the update process on a test cluster before you update the production cluster.
• Use the alternate disk migration installation process.
• Maintain the installed software at the same version and fix levels on all nodes in the cluster.