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

Chapter 13, Administering Cluster Functionality
Overview of Cluster Volume Management
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The private network allows the nodes to share information about system resources and
about each other’s state. Using the private network, any node can recognize which other
nodes are currently active, which are joining or leaving the cluster, and which have failed.
The private network requires at least two communication channels to provide
redundancy against one of the channels failing. If only one channel were used, its failure
would be indistinguishable from node failure—a condition known as network partitioning.
Example of a 4-Node Cluster
To the cluster monitor, all nodes are the same. VxVM objects configured within shared
disk groups can potentially be accessed by all nodes that join the cluster. However, the
cluster functionality of VxVM requires that one node act as the master node; all other nodes
in the cluster are slave nodes. Any node is capable of being the master node, and it is
responsible for coordinating certain VxVM activities.
Note You must run commands that configure or reconfigure VxVM objects on the master
node. Tasks that must be initiated from the master node include setting up shared
disk groups, creating and reconfiguring volumes, and performing snapshot
operations.
Redundant
SCSI or Fibre
Channel
Connectivity
Cluster-Shareable
Disks
Redundant Private Network
Node 0
(master)
Node 1
(slave)
Node 2
(slave)
Node 3
(slave)
Cluster-Shareable
Disk Groups