Designing Disaster Tolerant High Availability Clusters, 10th Edition, March 2003 (B7660-90013)

Building a Continental Cluster
Understanding Continental Cluster Concepts
Chapter 5188
Performing Cluster Recovery
When a CLUSTER_ALARM is issued, there may be a need for recovery, and
the recovery command, cmrecovercl, is enabled for use by the root user.
Cluster recovery is carried out at the site of the recovery cluster by using
the cmrecovercl command, as follows:
# cmrecovercl
This command will fail if a cluster alarm has not been issued. The
command has the effect of halting any data replication activity from the
failed cluster to the local cluster, and starting up on the local cluster all
the recovery packages that are pre-configured in recovery groups,
which are the units of recovery in a continental cluster.
If option “-g RecoveryGroup” is specified with the command, the
recovery process, halting of data replication activity and starting of
recovery package, will be done only for the specified recovery group.
After the cmrecovercl command is issued, there is a delay of at least 90
seconds per recovery group as the command makes sure that the package
is not active on another cluster.
Cluster recovery is done as a last resort, after all other approaches to
restore the unavailable cluster have been exhausted. It is important to
remember that cluster recovery sets in motion a process that cannot be
easily reversed. Unlike the failover of a package from one node to
another, failing a package from one cluster to another normally involves
a significant quantity of data that is being accessed from a new set of
disks. Returning control to the original cluster will involve
resynchronizing this data and resetting the roles of the clusters in a
process that is easier for some data replication techniques than others.
NOTE After a recovery, you cannot reverse directions and return a package to
its original cluster without first reconfiguring the data replication
hardware and/or software and synchronizing data. Therefore, you should
be very cautious when deciding to use the cmrecovercl command.
Notes on Packages in a Continental Cluster
Packages have somewhat different behavior in a continental cluster than
in a normal ServiceGuard environment. There are specific differences in