Managing Serviceguard 13th Edition, February 2007

Understanding Serviceguard Software Components
Serviceguard Architecture
Chapter 3 61
not standby LANs are configured. (For further discussion, see “What
Happens when a Node Times Out” on page 129. For advice on setting
HEARTBEAT_INTERVAL and NODE_TIMEOUT, see “Cluster Configuration
Parameters” on page 157.)
The cmcld daemon also monitors the health of the cluster networks and
performs local LAN failover. Finally, cmcld manages Serviceguard
packages, determining where to run them and when to start them.
NOTE The three central components of Serviceguard—Package Manager,
Cluster Manager, and Network Manager—run as parts of the cmcld
daemon. This daemon runs at priority 20 on all cluster nodes. It is
important that user processes should have a priority lower than 20,
otherwise they may prevent Serviceguard from updating the kernel
safety timer, causing a TOC.
File Management Daemon: cmfileassistd
The cmfileassistd daemon is used by cmcld to manage the files that it
needs to read from, and write to, disk. This is to prevent any delays in
issuing Input/Output from impacting the timing of cmcld.
Syslog Log Daemon: cmlogd
cmlogd is used by cmcld to write messages to syslog. Any message
written to syslog by cmcld it written through cmlogd. This is to prevent
any delays in writing to syslog from impacting the timing of cmcld.
Cluster Logical Volume Manager Daemon: cmlvmd
This daemon is responsible for keeping track of all the volume group(s)
that have been made cluster aware. When a volume group is made
cluster aware, a cluster node can only activate it in exclusive mode. This
prevents the volume group from being activated in write mode by more
than one node at a time.
Cluster Object Manager Daemon: cmomd
This daemon is responsible for providing information about the cluster to
clients—external products or tools such as the station-management
version of Serviceguard Manager (and the command-line version of the
“plug-in”) that depend on knowledge of the state of cluster objects.