VERITAS Volume Manager 4.1 Administrator's Guide

Administering Cluster Functionality
Cluster Initialization and Configuration
Chapter 10360
When a node joins the cluster, this information is automatically loaded
into VxVM on that node at node startup time.
NOTE The cluster functionality of VxVM requires that a cluster monitor (such
as provided by MC/ServiceGuard) has been configured. If
MC/ServiceGuard is chosen as your cluster monitor, no additional
configuration of VxVM is required, apart from the cluster configuration
requirements of MC/ServiceGuard.
The cluster monitor startup procedure effects node initialization, and
brings up the various cluster components (such as VxVM with cluster
support, the cluster monitor, and a distributed lock manager) on the
node. Once this is complete, applications may be started. The cluster
monitor startup procedure must be invoked on each node to be joined to
the cluster.
For VxVM in a cluster environment, initialization consists of loading the
cluster configuration information and joining the nodes in the cluster.
The first node to join becomes the master node, and later nodes (slaves)
join to the master. If two nodes join simultaneously, VxVM chooses the
master. Once the join for a given node is complete, that node has access
to the shared disks.
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 362) do not take place at the same time as cluster
reconfigurations. Depending on the circumstances, an operation may be