Managing Serviceguard Fifteenth Edition, reprinted May 2008

Understanding Serviceguard Software Components
Serviceguard Architecture
Chapter 362
You must also edit /etc/rc.config.d/cmsnmpagt to auto-start
cmsnmpd. Configure cmsnmpd to start before the Serviceguard cluster
comes up.
For more information, see the cmsnmpd (1m) manpage.
Service Assistant Daemon: cmsrvassistd
This daemon forks and execs any script or processes as required by the
cluster daemon, cmcld. There are two type of forks that this daemon
carries out:
• Executing package run and halt scripts
• Launching services
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.
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 cluster
lock. See “Cluster Quorum to Prevent Split-Brain Syndrome” and
“Cluster Lock” on page 68.
The quorum server, if used, runs on a system external to the cluster and
is started by the system administrator, not by Serviceguard. It is
normally started from /etc/inittab with the respawn option, which
means that it automatically restarts if it fails or is killed. 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, see the latest version of the HP Serviceguard Quorum Server
release notes at http://docs.hp.com -> High Availability ->
Quorum Server.