Veritas Volume Manager 4.1 Administrator's Guide (HP-UX 11i v3, February 2007)

Chapter 13, Administering Cluster Functionality
Cluster Initialization and Configuration
359
Note To make effective use of the cluster functionality of VxVM requires that you
configure a cluster monitor (such as provided by GAB (Group Membership and
Atomic Broadcast) in VCS).
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 disk groups and volumes.
Cluster Reconfiguration
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 informs VxVM for it to take appropriate action.
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 361) 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 “vxclustadm Utility” on page 359.
vxclustadm Utility
The vxclustadm command provides an interface to the cluster functionality of VxVM
when VCS is used as the cluster monitor. It is also called during cluster startup and
shutdown. In the absence of a cluster monitor, vxclustadm can also be used to activate
or deactivate the cluster functionality of VxVM on any node in a cluster.