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

6 Administering Metrocluster
Adding a node to Metrocluster
To add a node to Metrocluster with Continuous Access EVA:
1. To add the node in a cluster, edit the Serviceguard cluster configuration file, and then apply
the configuration:
# cmapplyconf -C cluster.config
2. Copy caeva.map file to the new node.
# rcp /etc/dtsconf/caeva.map <new_node_name>/etc/dtsconf/caeva.map
3. If node_name is set to “*” in Metrocluster package configuration, do the following:
a. Create the Metrocluster package directory on the newly added node.
b. Copy Metrocluster environment file from one of the existing nodes to the same pathname
on the newly added node.
# rcp <package_directory>/<Metrocluster_environment_file>
<new_node_name>:<package_directory>
4. If the node names are explicitly specified for node_name parameter in Metrocluster package
configuration, add the newly added node in a Metrocluster package by editing the Metrocluster
package configuration and applying the configuration:
# cmapplyconf –P <package_config_file>
Maintaining a Metrocluster using P6000 Continous Access replication
While the package is running, a manual storage failover on P6000 Continous Access outside
Metrocluster with Continous Access EVA software can cause the package to halt. HP recommends
that no manual storage failover be performed while the package is running.
A manual change of HP P6000/EVA Continuous Access link state from suspend to resume is
allowed to re-establish data replication while the package is running.
HP P6000/EVA Continuous Access Link failure scenarios
If all Continuous Access links fail and if failsafe mode is disabled, the application package continues
to run and writes new I/O to source Vdisk. The virtual log in P6000/EVA controller collects host
write commands and data; DR group's log state changes from normal to logging. When a DR
group is in a logging state, the log grows in proportion to the amount of write I/O being sent to
the source Vdisks. Upon Continuous Access links recovery, HP P6000/EVA Continuous Access
automatically normalizes the source Vdisk and destination Vdisk data. If the links are down for a
long time and failsafe mode is disabled, the log disk may be full, and full copy occurs automatically
upon link recovery.
If the log disk is not full, when a Continuous Access connection is re-established, the contents of
the log are written to the destination Vdisk to synchronize it with the source Vdisk. This process of
writing the log contents, in the order that the writes occurred, is called merging. While merging
is in progress, write ordering is maintained and hence the data on the destination Vdisk is consistent.
If the log disk is full, when a Continuous Access connection is re-established, a full copy from the
source Vdisk to the destination Vdisk is done. Since a full copy is done at the block level, the data
on the destination Vdisk is not consistent until the copy completes.
If primary site fails while copy is in progress, the data in destination Vdisk is not consistent, and
is not usable. The package can never startup on the recovery site. The application will not be online
until the primary site is restored. To manage the resynchronization and to ensure that a consistent
copy of data is there on recovery site, do the following:
60 Administering Metrocluster