Managing Serviceguard 14th Edition, June 2007

Understanding Serviceguard Software Components
Serviceguard Architecture
Chapter 3 57
from the expiration of the safety timer, messages will be written to
/var/adm/syslog/syslog.log and the kernel’s message buffer, and a
system dump is performed.
The duration of the safety timer depends on the cluster configuration
parameters HEARTBEAT_INTERVAL and NODE_TIMEOUT, and also on the
characteristics of the cluster configuration, such as whether it uses a
quorum server or a cluster lock (and what type of lock) and whether or
not standby LANs are configured. (For further discussion, see “What
Happens when a Node Times Out” on page 125. For advice on setting
HEARTBEAT_INTERVAL and NODE_TIMEOUT, see “Cluster Configuration
Parameters” on page 154.)
cmcld also manages Serviceguard packages, determining where to run
them and when to start them.
NOTE Two of the central components of Serviceguard—Package Manager, and
Cluster 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 system
reset.
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.