Cluster Aware concepts

When you create a cluster of a single node or multiple nodes, the interconnected set of nodes can leverage the Cluster Aware capabilities and services that are built into the AIX® operating system.

Applications can build on the tools and service capabilities that are provided when you create a cluster of nodes to make the application highly available and resilient.

Each node that is added to a cluster by using Cluster Aware must have common storage devices available, either through the storage area network (SAN) or through the serial-attached SCSI (SAS) subsystems. These storage devices are used for the cluster repository disk and for any clustered shared disks. The storage naming service does not provide a global device view.

A multicast address is used for cluster communications between the nodes in the cluster. Therefore, you need to review any network considerations before you create a cluster.

Each node must have at least one IP version 4 address configured on its network interface. The IP version 4 address is used as a basis for creating an IP version 4 multicast address, which the cluster communications uses for internal communications. You can configure IP version 6 addresses on any node or nodes in the cluster. These nodes support cluster monitoring of events and cluster configuration attributes.

Scalable reliable multicasting is implemented in the cluster with a special gossip protocol over the multicast address. The gossip protocol determines the node configuration and then transmits the gossip packets over all available networking and storage communication interfaces. If no storage communication interfaces are configured, only the traditional networking interfaces are used.

Using Cluster Aware you can monitor communications and network topology changes at various levels for all available services. With cluster monitoring, you can sense that a node is down, and a cluster can detect that a specific adapter is down or that a specific interface on an adapter is down.

A point-of-contact indicates that a node has actually received communication packets across this interface from another node. This communication process allows the application that is monitoring the health of a node to make discrete actions based on near real-time event notification. You can also monitor the storage devices to provide UP events and DOWN events for any recovery actions that are identified as necessary by the monitoring application.