Veritas Volume Manager 5.0 Administrator's Guide (September 2006)

401Administering cluster functionality
Cluster initialization and configuration
■ If the vxconfigd daemon is stopped on the master node, the vxconfigd
daemons on the slave nodes periodically attempt to rejoin to the master node. Such
attempts do not succeed until the vxconfigd daemon is restarted on the master. In
this case, the
vxconfigd daemons on the slave nodes have not lost information
about the shared configuration, so that any displayed configuration information is
correct.
■ If the vxconfigd daemon is stopped on a slave node, the master node takes no
action. When the vxconfigd daemon is restarted on the slave, the slave
vxconfigd daemon attempts to reconnect to the master daemon and to re-acquire
the information about the shared configuration. (Neither the kernel view of the shared
configuration nor access to shared disks is affected.) Until the vxconfigd daemon
on the slave node has successfully reconnected to the vxconfigd daemon on the
master node, it has very little information about the shared configuration and any
attempts to display or modify the shared configuration can fail. For example, shared
disk groups listed using the
vxdg list command are marked as disabled; when
the rejoin completes successfully, they are marked as enabled.
■ If the vxconfigd daemon is stopped on both the master and slave nodes, the slave
nodes do not display accurate configuration information until vxconfigd is
restarted on the master and slave nodes, and the daemons have reconnected.
Note: The -r reset option to vxconfigd restarts the vxconfigd daemon and recreates
all states from scratch. This option cannot be used to restart
vxconfigd while a node is
joined to a cluster because it causes cluster information to be discarded.
Node shutdown
VxVM supports clean node shutdown, which allows a node to leave the cluster gracefully
when all access to shared volumes has ceased. The host is still operational, but cluster
applications cannot be run on it.
The cluster functionality of VxVM maintains global state information for each volume.
This enables VxVM to determine which volumes need to be recovered when a node
crashes. When a node leaves the cluster due to a crash or by some other means that is not
clean, VxVM determines which volumes may have writes that have not completed and the
master node resynchronizes these volumes. It can use dirty region logging (DRL) or
FastResync if these are active for any of the volumes.
Clean node shutdown must be used after, or in conjunction with, a Serviceguard
cmhaltnode command, which halts all cluster applications. Depending on the
characteristics of the clustered application and its shutdown procedure, a successful
shutdown can require a lot of time (minutes to hours). For instance, many applications
have the concept of draining, where they accept no new work, but complete any work in