HP Serviceguard manual Heartbeat Messages, Manual Startup of Entire Cluster

Documenting an HA Cluster ” (page 92)). You can set cluster parameters using Serviceguard Manager or by editing the cluster configuration file (see Chapter 5: “Building an HA Cluster Configuration” (page 158)). 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 69).)

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” (page 88) . At the end of the re-formation, information about the new cluster membership is passed to the package coordinator (described further in this chapter, in “How the Package Manager Works” (page 50)). Failover packages that were running on nodes that are no longer in the new cluster are transferred to their adoptive nodes.

If heartbeat and data are sent over the same LAN subnet, data congestion may cause Serviceguard to miss heartbeats and initiate a cluster re-formation that would not otherwise have been needed. For this reason, HP recommends that you dedicate a LAN for the heartbeat as well as configuring heartbeat over the data network.

NOTE: You can no longer run the heartbeat on a serial (RS232) line or an FDDI or Token Ring network.

Each node sends its heartbeat message at a rate calculated by Serviceguard on the basis of the value of the MEMBER_TIMEOUT parameter, set in the cluster configuration file, which you create as a part of cluster configuration.

IMPORTANT: When multiple heartbeats are configured, heartbeats are sent in parallel; Serviceguard must receive at least one heartbeat to establish the health of a node. HP recommends that you configure all subnets that connect cluster nodes as heartbeat networks; this increases protection against multiple faults at no additional cost.

Heartbeat IP addresses are usually on the same subnet on each node, but it is possible to configure a cluster that spans subnets; see “Cross-Subnet Configurations” (page 30).

For more information about heartbeat requirements, see the entry for HEARTBEAT_IP, under “Cluster Configuration Parameters ”. For timeout requirements and recommendations, see the MEMBER_TIMEOUT parameter description in the same section. For troubleshooting information, see “Cluster Re-formations Caused by MEMBER_TIMEOUT Being Set too Low” (page 333). See also “Cluster Daemon: cmcld” (page 41).

Manual Startup of Entire Cluster

A manual startup forms a cluster out of all the nodes in the cluster configuration. Manual startup is normally done the first time you bring up the cluster, after cluster-wide maintenance or upgrade, or after reconfiguration.

Before startup, the same binary cluster configuration file must exist on all nodes in the cluster. The system administrator starts the cluster in Serviceguard Manager or with the cmruncl command issued from one node. The cmruncl command can only be used when the cluster is not running, that is, when none of the nodes is running the cmcld daemon.

During startup, the cluster manager software checks to see if all nodes specified in the startup command are valid members of the cluster, are up and running, are attempting to form a cluster, and can communicate with each other. If they can, then the cluster manager forms the cluster.

How the Cluster Manager Works 45