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416 Administering cluster functionality
Cluster initialization and configuration
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.
In an HP Serviceguard cluster, use the equivalent Serviceguard functionality to
stop and restart the appropriate package.
Node shutdown
Although it is possible to shut down the cluster on a node by invoking the
shutdown procedure of the node’s cluster monitor, this procedure is intended
for terminating cluster components after stopping any applications on the node
that have access to shared storage. 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 procedure to
halt 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 progress
before exiting. This process can take a long time if, for example, a long-running
transaction is active.
When the VxVM shutdown procedure is invoked, it checks all volumes in all
shared disk groups on the node that is being shut down. The procedure then
either continues with the shutdown, or fails for one of the following reasons:
■ If all volumes in shared disk groups are closed, VxVM makes them
unavailable to applications. Because all nodes are informed that these
volumes are closed on the leaving node, no resynchronization is performed.
■ If any volume in a shared disk group is open, the shutdown operation in the
kernel waits until the volume is closed. There is no timeout checking in this
operation.