Veritas Volume Manager 5.0.1 Administrator's Guide, HP-UX 11i v3, First Edition, November 2009

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.
VxVM determines that the first node to join a cluster performs the function of
master node. If the master node leaves a cluster, one of the slave nodes is chosen
to be the new master.
Private and shared disk groups
The following types of disk groups are defined:
Belongs to only one node. A private disk group can only be imported
by one system. Disks in a private disk group may be physically
accessible from one or more systems, but access is restricted to one
system only.
The boot disk group (usually aliased by the reserved disk group name
bootdg) is always a private disk group.
Private disk group
Can be shared by all nodes. A shared (or cluster-shareable) disk group
is imported by all cluster nodes. Disks in a shared disk group must be
physically accessible from all systems that may join the cluster.
Shared disk group
In a cluster, most disk groups are shared. Disks in a shared disk group are
accessible from all nodes in a cluster, allowing applications on multiple cluster
nodes to simultaneously access the same disk. A volume in a shared disk group
can be simultaneously accessed by more than one node in the cluster, subject to
licensing and disk group activation mode restrictions.
You can use the vxdg command to designate a disk group as cluster-shareable.
See “Importing disk groups as shared” on page 479.
When a disk group is imported as cluster-shareable for one node, each disk header
is marked with the cluster ID. As each node subsequently joins the cluster, it
recognizes the disk group as being cluster-shareable and imports it. As system
administrator, you can also import or deport a shared disk group at any time; the
operation takes place in a distributed fashion on all nodes.
Each physical disk is marked with a unique disk ID. When cluster functionality
for VxVM starts on the master, it imports all shared disk groups (except for any
that do not have the autoimport attribute set). When a slave tries to join a cluster,
the master sends it a list of the disk IDs that it has imported, and the slave checks
to see if it can access them all. If the slave cannot access one of the listed disks,
it abandons its attempt to join the cluster. If it can access all of the listed disks,
455Administering cluster functionality
Overview of cluster volume management