HP P6000 Continuous Access Implementation Guide (T3680-96431, August 2012)

Procedure:
To resume operation if you are unable to access the destination in failsafe mode:
1. Change affected DR groups from failsafe-enabled mode to normal mode.
2. If necessary, issue operating system commands to the local hosts to restart I/O on the virtual
disks that were failsafe-locked. See “Resuming host I/O after failover” (page 118).
3. When connections to the destination are re-established, control the merging of data at the
destination by suspending replication on the less important DR groups. This forces the controllers
to replicate the most important data first when the links to the destination are re-established.
For more information, see “Throttling a merge I/O after logging” (page 124).
NOTE:
If DR groups are suspended for an extended amount of time, the log can run out of space.
Restoring the connection to the destination array initiates a normalization of these DR groups.
During the normalization operation, the data is inconsistent at the destination.
4. When merging is complete, change DR groups from normal mode to failsafe-enabled mode,
if desired.
NOTE: Once a DR group starts a normalization, you can enable failsafe mode for that DR group.
Failback to the original source following a planned or unplanned failover
Scenario: You are operating from an array that is not the original source (it's not designated as
“Home” in HP P6000 Replication Solutions Manager). You need to move operations from the
destination array back to the source array.
Action summary: Prepare the source array for the failover and fail over the DR group. Failback
(also known as reverting to Home) is identical to a planned failover. Fifteen minutes after failing
over from a source to a destination array, you can fail back in the other direction.
Procedure:
To fail back to the original source:
1. If desired, move storage management to another management server. For instructions, see
the HP P6000 Command View User Guide.
2. Properly shut down all applications, and then shut down the servers. Ensure the server has
properly flushed all internally cached data. Failure to do this will result in a loss of data cached
on the server.
3. Ensure that all DR groups have resumed and are fully normalized or merged. If a DR group
is merging or a normalization is in progress, wait for the process to complete.
4. Fail over the DR groups (or revert to Home using HP P6000 Replication Solutions Manager).
5. Issue operating system commands to resume I/O to the new (original) source. See “Resuming
host I/O after failover” (page 118).
Return operations to new hardware
NOTE: This section assumes a failure of the array hardware only and does not provide information
for recovering from a site disaster that includes the failure and replacement of other hardware such
as servers.
Scenario: Some type of disaster damaged local equipment and forced a failover to a remote site.
Hardware on the local source array was replaced. The new hardware now acts as the destination
array; you are operating from an array that is not the original source (designated as Home).
Action summary: When the site is back online, fail over to new hardware at the local site.
Figure 56 (page 111) illustrates the steps to return operations to new hardware.
110 Failover and recovery