Managing HP Serviceguard for Linux Ninth Edition, April 2009

For services, cmcld monitors the service process and, depending on the number of
service retries, cmcld either restarts the service through cmsrvassistd or it causes
the package to halt and moves the package to an available alternate node. The path for
this daemon is: $SGLBIN/cmserviced.
Quorum Server Daemon: qs
Using a quorum server is one way to break a tie and establish a quorum when the
cluster is re-forming; the other way is to use a Lock LUN. See “Cluster Quorum to
Prevent Split-Brain Syndrome” (page 44) and the sections that follow it.
The quorum server, if used, runs on a system external to the cluster. It is normally
started from /etc/inittab with the respawn option, which means that it
automatically restarts if it fails or is killed. It can also be configured as a Serviceguard
package in a cluster other than the one(s) it serves; see Figure 3-4 (page 47).
All members of the cluster initiate and maintain a connection to the quorum server; if
it dies, the Serviceguard nodes will detect this and then periodically try to reconnect
to it. If there is a cluster re-formation while the quorum server is down and tie-breaking
is needed, the re-formation will fail and all the nodes will halt (system reset). For this
reason it is important to bring the quorum server back up as soon as possible.
For more information about the Quorum Server software and how it works, including
instructions for configuring the Quorum Server as a Serviceguard package, see the
latest version of the HP Serviceguard Quorum Server release notes at
http://docs.hp.com -> High Availability -> Quorum Server. See also
“Use of the Quorum Server as a Cluster Lock” (page 46).
The path for this daemon is:
• For SUSE: /opt/qs/bin/qs
• For Red Hat: /usr/local/qs/bin/qs
Utility Daemon: cmlockd
Runs on every node on which cmcld is running. It maintains the active and pending
cluster resource locks.
Cluster SNMP Agent Daemon: cmsnmpd
This daemon collaborates with the SNMP Master Agent to provide instrumentation
for the cluster Management Information Base (MIB).
The SNMP Master Agent and the cmsnmpd provide notification (traps) for
cluster-related events. For example, a trap is sent when the cluster configuration changes,
or when a Serviceguard package has failed. To configure the agent to send traps to one
or more specific destinations, add the trap destinations to
/etc/snmp/snmptrapd.conf (SUSE and Red Hat). Make sure traps are turned on
with trap2sink in /etc/snmp/snmpd.conf (SUSE and Red Hat).
Serviceguard Architecture 41