Below is a quick list of some of the key AIX concept terminology.
Loosely-coupled collection of independent systems (nodes) or logical partitions (LPARs) organized into a network for the purpose of sharing resources and communicating with each other.
PowerHA defines relationships among cooperating systems where peer cluster nodes provide the services offered by a cluster node if that node is unable to do so. These individual nodes are together responsible for maintaining the functionality of one or more applications in case of a failure of any cluster component.
An IBM Power (System p, System i®, or BladeCenter) system (or LPAR) running AIX and PowerHA that is defined as part of a cluster. Each node has a collection of resources (disks, file systems, IP addresses, and applications) that can be transferred to another node in the cluster in case the node or a component fails.
A client is a system that can access the application running on the cluster nodes over a local area network (LAN). Clients run a client application that connects to the server (node) where the application runs.
Contains basic cluster components nodes, networks, communication interfaces, and communication adapters.
Logical components or entities that are being made highly available (for example, file systems, raw devices, service IP labels, and applications) by being moved from one node to another. All resources that together form a highly available application or service, are grouped together in resource groups (RG).
PowerHA keeps the RG highly available as a single entity that can be moved from node to node in the event of a component or node failure. Resource groups can be available from a single node or, in the case of concurrent applications, available simultaneously from multiple nodes. A cluster can host more than one resource group, thus allowing for efficient use of the cluster nodes.
Service IP label
A label that matches to a service IP address and is used for communications between clients and the node. A service IP label is part of a resource group, which means that PowerHA can monitor it and keep it highly available.
IP address takeover (IPAT)
The process whereby an IP address is moved from one adapter to another adapter on the same logical network. This adapter can be on the same node, or another node in the cluster. If aliasing is used as the method of assigning addresses to adapters, then more than one address can reside on a single adapter.
This is the operation of transferring resources between nodes inside the cluster. If one component or node fails because of a hardware or operating system problem, its resource groups are moved to the another node.
This represents the movement of a resource group from one active node to another node (backup node) in response to a failure on that active node.
This represents the movement of a resource group back from the backup node to the previous node, when it becomes available. This movement is typically in response to the reintegration of the previously failed node.
A packet sent between communication interfaces in the cluster, used by the various cluster daemons to monitor the state of the cluster components (nodes, networks, adapters).
These consist of two types of processes (topology and group services) that monitor the state of the cluster and each node. The cluster manager receives event information generated by these daemons and takes corresponding (response) actions in case of any failure.
The node with the highest IP address as defined in one of the PowerHA networks (the first network available), that acts as the central repository for all topology and group data coming from the RSCT daemons concerning the state of the cluster.
Group leader backup
This is the node with the next highest IP address on the same arbitrarily chosen network, that acts as a backup for the group leader. It takes over the role of group leader in the event that the group leader leaves the cluster.
A node chosen by the RSCT group leader (the node with the next highest IP address after the group leader backup), if such exists, else it is the group leader backup itself. The mayor is responsible for informing other nodes of any changes in the cluster as determined by the group leader.