Overview of H ANFS for AIX
HANFS for AIX Cluster Hardware Components
HANFS for AIX Installation and Administration Guide 1-3
• Serial network—Provides a point-to-point connection between two cluster nodes used by
HANFS for AIX for control messages and heartbeat traffic should the TCP/IP subsystem
fail. A serial network can be a SCSI-2 Differential bus using target mode SCSI or an RS232
serial line.
Network Adapters
Typically, a node should have at least two network adapters—a service adapter and a standby
adapter—for each connected network. For serial or SP Switch networks, however, this
requirement does not apply.
Service network adapter—Primary connection between a node and a network. A node has one
service network adapter for each physical network to which it connects. This adapter is used for
cluster TCP/IP traffic. Its address is published by the Cluster Information Program (Clinfo) to
application programs that want to use cluster services.
• Standby network adapter—Backs up a service network adapter. The service network
adapter can be on the local node or on the remote node (since address takeover must be
enabled). If a service network adapter on the local node fails, the HANFS for AIX software
swaps the standby network address with the service network address. If the remote node
fails, the standby network adapter on the l ocal node assumes the IP address of the service
network adapter on the failed node.
Note: In clusters defined on SP systems, you do not need standby adapters
for the SP Switch. The SP Switch uses IP address aliasing to permit IP
address takeover. For more information, see Chapter C, Installing and
Configuring HANFS for AIX on RS/6000 SPs.
Assigning a Boot Adapter Label for IP Address Takeover
IP address takeover (IPAT) is an AIX facility that allows one node to acquire the network
address of another node in the cluster. The HANFS for A IX software requires that IPAT be
enabled. For IPAT to work correctly, you must assign a boot adapter label to the service adapter
on each cluster node. Nodes use the boot adapter label after a system reboot and before the
HANFS for AIX software is started.
When HANFS for AIX is started on a node, the node’s service adapter is reconfigured to use
the service label (address) instead of the boot label. If this node should fail, the takeover node
acquires the failed node’s service address on its standby adapter, making the failure transparent
to clients using that specific service address.
During the reintegration of the failed node, which comes up on its boot address, the t akeover
node will release the service address it acquired from the failed node. Afterwards, the
reintegrating node will reconfigure its boot address to its reacquired service address.
• It is important to realize that the boot address does not use a separate physical adapter, but
instead is a second name and IP address associated with a service adapter. All cluster nodes
must have this entry in the local /etc/hosts file and, if applicable, in the nameserver
configuration.