Building Disaster Recovery Serviceguard Solutions Using Metrocluster with Continuous Access EVA A.05.01

4 Additional Metrocluster features
Data replication storage failover preview
In an actual failure, packages are failed over to the standby site. In package startup, the underlying
storage is failed over based on the parameters defined in Metrocluster environment file. The storage
failover might fail under the following conditions:
• Incorrect configuration or setup of Metrocluster and data replication environment.
The storage failover can fail if the Metrocluster Environment file contains syntax errors, or
invalid parameter values, or the installed Metrocluster binaries are corrupt or have incorrect
file permissions or the SMI-S server is unreachable or caeva.map file is corrupted.
• Invalid data replication state.
The data may not be in write-order due to a track copy at the time of the failover attempt.
Also, the data is not current (lagging behind the primary) and the Metrocluster environment
variables are not set correctly to allow a failover on non-current data.
The command cmdrprev previews the failover of data replication storage. It determines if storage
failover can be successful during an actual package failover. This command can be used in both
Metrocluster and Continentalclusters. If the preview fails, the cmdrprev command displays a
detailed log that lists the cause for failure in stdout. The command options are as follows:
cmdrprev {-p <package> |-e <Metrocluster environment file>}
For more information, see the cmdrprev manpage.
The command exit value indicates if the storage failover in an actual package will succeed or not.
Table 4 describes the exit values of the command.
Table 4 Command exit value and its description
DescriptionValue
The data replication storage failover preview failed. This indicates that in the event of an
actual recovery process, the data replication storage failover will not succeed on any node
in the cluster.
-1
The failure is due to invalid command usage or due to invalid input parameters.
The data replication storage failover preview is successful on the node where the command
is run.
0
This indicates if data replication storage failover will be successful in the event of a package
failover.
The data replication storage failover preview failed.1
This indicates that in the event of an actual recovery process, the data replication storage
failover will not succeed on any node in the cluster.
The data replication storage failover preview failed due to node specific error conditions or
due to transient conditions.
2
This indicates that in the event of an actual recovery process, the data replication storage
failover will not succeed on that node. Failover may be successful you attempt at a later time
or attempt on a different node in the cluster.
Cluster verification
Starting from HP Serviceguard version A.11.20, the cmcheckconf -v command validates the
cluster and the package configuration. Starting from the April 2011 patch release, Metrolcuster
uses this functionality to ensure the sanity of Metrocluster and the Site Controller package
configurations. HP recommends you to set up a cron job to run the cmcheckconf command
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