General network considerations for PowerHA SystemMirror

PowerHA® SystemMirror® allows internode communication with Ethernet networks.

IP aliases
An IP alias is an IP label or address that is configured onto a network interface controller (NIC) in addition to the normally configured IP label or address on the NIC. The use of IP aliases is an AIX® function that PowerHA SystemMirror supports. AIX® supports multiple IP aliases on a NIC. Each IP alias on a NIC can be on a separate subnet. AIX® also allows IP aliases with different subnet masks to be configured for an interface. PowerHA SystemMirror does not yet support this function.
Network connections
PowerHA SystemMirror requires that each node in the cluster have at least one direct, nonrouted network connection with every other node. The software uses these network connections to pass heartbeat messages among the cluster nodes to determine the state of all cluster nodes, networks, and network interfaces.
IP labels
In a environment that is not using PowerHA SystemMirror, a host name typically identifies a system, with the host name also being the IP label of one of the network interfaces in the system. Thus, a system can be reached by using its host name as the IP label for a connection.
Cluster partitioning
Partitioning, also called node isolation, occurs when a network or network interface controller (NIC) failure isolates cluster nodes from each other.
Example: General network connection
An example of correct PowerHA SystemMirror networking consists of two separate Ethernet networks, each with two network interfaces on each node.
PowerHA SystemMirror configuration in switched networks
If the networks and the switches are incorrectly defined or configured, unexpected network interface failure events can occur in PowerHA SystemMirror configurations that use switched networks.
PowerHA SystemMirror and virtual Ethernet
PowerHA SystemMirror supports virtual Ethernet provided by the Virtual I/O Server (VIOS) or integrated virtual Ethernet (IVE) facilities, with the applicable APARs installed. The PowerHA SystemMirror support is identical for VIOS and IVE.

Parent topic: Planning cluster network connectivity