VERITAS Volume Manager 3.5 Administrator's Guide (September 2004)

Administering Cluster Functionality
Cluster Initialization and Configuration
Chapter 10350
example, vxconfigd rejects an attempt to create a new disk group with
the same name as an existing disk group. The vxconfigd daemon on the
master node then sends details of the changes to the vxconfigd daemons
on the slave nodes. The vxconfigd daemons on the slave nodes then
perform their own checking. For example, each slave node checks that it
does not have a private disk group with the same name as the one being
created; if the operation involves a new disk, each node checks that it can
access that disk. When the vxconfigd daemons on all the nodes agree
that the proposed change is reasonable, each notifies its kernel. The
kernels then cooperate to either commit or to abandon the transaction.
Before the transaction can be committed, all of the kernels ensure that
no I/O is underway. The master node is responsible both for initiating the
reconfiguration, and for coordinating the commitment of the transaction.
The resulting configuration changes appear to occur simultaneously on
all nodes.
If a vxconfigd daemon on any node goes away during reconfiguration,
all nodes are notified and the operation fails. If any node leaves the
cluster, the operation fails unless the master has already committed it. If
the master node leaves the cluster, the new master node, which was
previously a slave node, completes or fails the operation depending on
whether or not it received notification of successful completion from the
previous master node. This notification is performed in such a way that if
the new master does not receive it, neither does any other slave.
If a node attempts to join a cluster while a volume reconfiguration is
being performed, the result of the reconfiguration depends on how far it
has progressed. If the kernel has not yet been invoked, the volume
reconfiguration is suspended until the node has joined the cluster. If the
kernel has been invoked, the node waits until the reconfiguration is
complete before joining the cluster.
When an error occurs, such as when a check on a slave fails or a node
leaves the cluster, the error is returned to the utility and a message is
sent to the console on the master node to identify on which node the error
occurred.
vxconfigd Daemon
The VxVM configuration daemon, vxconfigd, maintains the
configuration of VxVM objects. It receives cluster-related instructions
from the kernel. A separate copy of vxconfigd runs on each node, and
these copies communicate with each other over a network. When
invoked, a VxVM utility communicates with the vxconfigd daemon