Managing Serviceguard Nineteenth Edition, Reprinted June 2011

Veritas CFS components operate directly over Ethernet networks that connect the nodes within a
cluster. Redundant networks are required to avoid single points of failure.
The Veritas CFS components are:
• GAB (Group Membership Services/Atomic Broadcast) — When Veritas Cluster Volume
Manager (CVM) 4.1 or later, or Veritas Cluster File System (CFS), is deployed as part of the
Serviceguard Storage Management Suite bundles, the file /etc/gabtab is automatically
configured and maintained by Serviceguard.
GAB provides membership and messaging for CVM and the CFS. GAB membership also
provides orderly startup and shutdown of the cluster file system.
• LLT (Low Latency Transport) - When Veritas CVM or CFS is deployed as part of the Serviceguard
Storage Management Suite bundles, the LLT files/etc/llthosts and /etc/llttab are
automatically configured and maintained by Serviceguard.
LLT provides kernel-to-kernel communications and monitors network communications for CFS.
• vxfend - When Veritas CFS is deployed as part of the Serviceguard Storage Management
Suite, the I/O fencing daemon vxfend is also included. It implements a quorum-type
functionality for the Veritas Cluster File System. vxfend is controlled by Serviceguard to
synchronize quorum mechanisms.
• cmvxd - The Serviceguard-to-Veritas daemon coordinates the membership information between
Serviceguard and Veritas' Clustered File System product. (Only present when Veritas CFS is
installed.)
• cmvxping- The Serviceguard-to-Veritas daemon activates certain subsystems of the Veritas
Clustered File System product. (Only present when Veritas CFS is installed.)
How the Cluster Manager Works
The cluster manager is used to initialize a cluster, to monitor the health of the cluster, to recognize
node failure if it should occur, and to regulate the re-formation of the cluster when a node joins or
leaves the cluster. The cluster manager operates as a daemon process that runs on each node.
During cluster startup and re-formation activities, one node is selected to act as the cluster coordinator
. Although all nodes perform some cluster management functions, the cluster coordinator is the
central point for inter-node communication.
Configuring the Cluster
The system administrator sets up cluster configuration parameters and does an initial cluster startup;
thereafter, the cluster regulates itself without manual intervention in normal operation. Configuration
parameters for the cluster include the cluster name and nodes, networking parameters for the cluster
heartbeat, cluster lock information, and timing parameters (discussed in the chapter “Planning and
Documenting an HA Cluster ” (page 88)). You can set cluster parameters using Serviceguard
Manager or by editing the cluster configuration file (see Chapter 5: “Building an HA Cluster
Configuration” (page 149)). The parameters you enter are used to build a binary configuration file
which is propagated to all nodes in the cluster. This binary cluster configuration file must be the
same on all the nodes in the cluster.
Heartbeat Messages
Central to the operation of the cluster manager is the sending and receiving of heartbeat messages
among the nodes in the cluster. Each node in the cluster exchanges UDP heartbeat messages with
every other node over each monitored IP network configured as a heartbeat device. (LAN monitoring
is discussed later, in the section “Monitoring LAN Interfaces and Detecting Failure: Link Level”
(page 66).)
If a cluster node does not receive heartbeat messages from all other cluster nodes within the
prescribed time, a cluster re-formation is initiated; see “What Happens when a Node Times Out”
42 Understanding Serviceguard Software Components