Building Disaster Recovery Serviceguard Solutions Using Continentalclusters for Linux B.01.00.00

Maintaining Metrocluster with Continuous Access EVA P6000 for Linux data replication
environment
While the package is running, the package might halt because of unexpected conditions in the
Continuous Access EVA volumes caused by a manual storage failover on Continuous Access EVA
outside of Metrocluster Continuous Access EVA software. HP recommends that manual storage
failover must not be performed while the package is running.
A manual change of Continuous Access EVA link state from suspend to resume is allowed to
re-establish data replication while the package is running.
Continuous Access EVA Link Suspend and Resume Modes
Upon Continuous Access links recovery, Continuous Access EVA automatically normalizes (the
Continuous Access EVA term for “synchronizes”) the source Vdisk and destination Vdisk data.
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. Since write ordering
is maintained, the data on the destination Vdisk is consistent while merging is in progress.
If the log disk is full, when a Continuous Access connection is re-established, a full copy from the
source Vdisk is done to the destination Vdisk. Since a full copy is done at the block level, the data
on the destination Vdisk is not consistent until the copy completes.
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 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. If the links are down for a long time, the log disk might be full, and full copy happens
automatically upon link recovery. If primary site fails while copy is in progress, the data in destination
Vdisk is not consistent, and is not usable. To prevent this, after all the Continuous Access links fail,
HP recommends manually setting the Continuous Access link state to suspend mode by using the
Command View EVA UI. When Continuous Access link is in suspend state, Continuous Access
EVA does not try to normalize the source and destination Vdisks upon links recovery until you
manually change the link state to resume mode.
Maintaining 3PAR Remote Copy data replication environment
While the package is running, a manual storage failover on Remote Copy volume group outside
of Metrocluster with 3PAR Remote Copy software can cause the package to halt due to unexpected
condition of the 3PAR Remote Copy virtual volumes. HP recommends that no manual storage
failover be performed while the package is running.
If the Remote Copy replication was stopped due to link failures, you can manually start the
replication even while the package is running. You do not have to manually start the replication
if the auto_recover option is set for the Remote Copy volume group.
Viewing the Remote Copy volume group details
To associate the Remote Copy volume group name with the package, run the cmgetpkgenv
command:
# cmgetpkgenv <pkg_name>
To list the various properties of 3PAR Remote Copy volume group, run the CLI command showrcopy
command.
You can view the Remote Copy volume group details using HP 3PAR Management Console.
Maintaining the data replication environment 49