VERITAS Volume Manager 3.5 Administrator's Guide (September 2004)

Administering Cluster Functionality
Cluster Initialization and Configuration
Chapter 10348
Cluster Reconfiguration
A cluster reconfiguration occurs if a node leaves or joins a cluster.
Each node’s cluster monitor continuously watches the other cluster
nodes. When the membership of the cluster changes, the cluster monitor
calls the vxclustd cluster reconfiguration daemon. The vxclustd
daemon coordinates cluster reconfigurations and provides
communication between VxVM and the cluster monitor.
During cluster reconfiguration, VxVM suspends I/O to shared disks. I/O
resumes when the reconfiguration completes. Applications may appear
to freeze for a short time during reconfiguration.
If other operations, such as VxVM operations or recoveries, are in
progress, cluster reconfiguration can be delayed until those operations
have completed. Volume reconfigurations (see “Volume Reconfiguration”
on page 349) do not take place at the same time as cluster
reconfigurations. Depending on the circumstances, an operation may be
held up and restarted later. In most cases, cluster reconfiguration takes
precedence. However, if the volume reconfiguration is in the commit
stage, it completes first.
For more information on cluster reconfiguration, see “vxclustd Daemon”
on page 348
vxclustd Daemon
The vxclustd daemon is the VxVM cluster reconfiguration daemon. The
vxclustd daemon provides communication between the cluster monitor
and VxVM, and initiates cluster reconfiguration. Every node currently in
the cluster runs an instance of the vxclustd daemon. Whenever cluster
membership changes, the cluster monitor notifies the vxclustd daemon,
which then initiates a reconfiguration within VxVM.
The vxclustd daemon is started up by the cluster monitor when the node
initially attempts to join the cluster. The vxclustd daemon first registers
with the cluster monitor and obtains the following information from the
cluster monitor:
• cluster ID and cluster name
• node IDs and hostnames of all configured nodes
• IP addresses of the network interfaces through which the nodes
communicate with each other