VERITAS Volume Manager 3.5 Administrator's Guide (September 2002)

Cluster Initialization and Configuration
252 VERITAS Volume Manager Administrator’s Guide
Cluster Initialization and Configuration
Before any nodes can join a new cluster for the first time, you must supply certain
configuration information during cluster monitor setup. This information is normally
stored in some form of cluster monitor configuration database. The precise content and
format of this information depends on the characteristics of the cluster monitor. The
information required by VxVM is as follows:
◆ cluster ID
◆ node IDs
◆ network addresses of nodes
◆ port addresses
When anode joins the cluster, thisinformation is automatically loaded into VxVMon that
node at node startup time.
Note The cluster functionality ofVxVM 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, VxVMchooses the master. Oncethe join foragiven nodeiscomplete, 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.