Veritas Storage Foundation 5.0 for Oracle RAC Configuration Guide Extracts for HP Serviceguard Storage Management Suite, Second Edition, May 2008

Introducing Serviceguard Extension for RAC

Cluster Interconnect Communication Channel

Chapter 1

Cluster Membership

At a high level, all nodes configured by the installer can operate as a cluster; these nodes

form a cluster membership. In SGeRAC, a cluster membership specifically refers to all

systems configured with the same cluster ID communicating by way of a redundant

cluster interconnect. Refer to Using Serviceguard Extension for RAC for additional

information.

All nodes in a distributed system, such as SGeRAC, must remain constantly alert to the

nodes currently participating in the cluster. Nodes can leave or join the cluster at any

time because of shutting down, starting up, rebooting, powering off, or faulting

processes. SGeRAC uses its cluster membership capability to dynamically track the

overall cluster topology.

SGeRAC uses LLT heartbeats to determine cluster membership:

• When systems no longer receive heartbeat messages from a peer for a predetermined

interval, a protocol excludes the peer from the current membership.

• GAB informs processes on the remaining nodes that the cluster membership has

changed; this action initiates recovery actions specific to each module. For example,

CVM must initiate volume recovery and CFS must perform a fast parallel file system

check.

• When systems start receiving heartbeats from a peer outside of the current

membership, a protocol enables the peer to join the membership.

Cluster Communications

GAB provides reliable cluster communication between SGeRAC modules. GAB provides

guaranteed delivery of point-to-point messages and broadcast messages to all nodes.

Point-to-point messaging involves sending and acknowledging the message.

Atomic-broadcast messaging ensures all systems within the cluster receive all messages.

If a failure occurs while transmitting a broadcast message, GAB ensures all systems

have the same information after recovery.