2.1.2.4 Node Shutdown

The system administrator can shut down the cluster on a given node by invoking the cluster manager shutdown procedure on that node. This terminates cluster components after cluster applications have been stopped. CVM supports clean node shutdown, which is the ability of 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.

CVM maintains global state information for each volume. This enables CVM to accurately determine which volumes need recovery when a node crashes. When a node leaves the cluster due to a crash or by some other means that is not clean, CVM determines which volumes can have writes that have not completed and the master resynchronizes those volumes. If Dirty Region Logging (DRL) is active for any of those volumes, it will be used.

Clean node shutdown should 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, it can be a long time before the shutdown is successful (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 instance, a long-running transaction is active.

When the CVM shutdown procedure is invoked, it checks all volumes in all shared disk groups on the node that is being shut down and then either proceeds with the shutdown or fails:

• If all volumes in shared disk groups are closed, CVM makes them unavailable to applications. Since it is known on all nodes that these volumes are closed on the leaving node, no resynchronizations are performed.

• If any volume in a shared disk group is open, the CVM shutdown procedure returns failure. The shutdown procedure can be retried repeatedly until it succeeds. There is no timeout checking in this operation--it is intended as a service that verifies that the clustered applications are no longer active.

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  Note -

  Once the shutdown has succeeded and the node has left the cluster, it is not possible to access the shared volumes until it joins the cluster again.

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  Since shutdown can be a lengthy process, other reconfigurations can take place while shutdown is in progress. Normally, the shutdown attempt is suspended until the other reconfiguration completes. However, if it is too far advanced, the shutdown can complete first.