Managing Serviceguard 12th Edition, March 2006

Understanding Serviceguard Software Components
Serviceguard Architecture
Chapter 360
update the kernel timer, indicating a kernel hang. Before a TOC due to
the expiration of the safety timer, messages will be written to
/var/adm/syslog/syslog.log and the kernel’s message buffer.
The cmcld daemon also detects the health of the networks on the system
and performs local lan failover. Finally, this daemon handles the
management of 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 lower priority than 20,
otherwise they might prevent Serviceguard from updating the kernel
safety timer, thus causing the node to undergo 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 Serviceguard Manager that
depend on knowledge of the state of cluster objects. Clients send queries