Building Disaster Recovery Serviceguard Solutions Using Metrocluster with Continuous Access for P9000 and XP A.11.00

Figure 46 Package Failover with data being replicated to DC3 from DC1
NOTE: When the application package is running on DC1 and the data is being replicated to
DC3 from DC1 (i.e. Multi-Target topology) as shown in Figure 9, upon the failure of all nodes in
DC1, the application package fails over to a node in DC2. As part of the package startup, the
data replication between DC1 and DC2 is reversed and the data starts replicating from DC2 to
DC1. This suspends the Active-CAJ pair internally by the firmware. In this case of all DC1 nodes
failed, 3DC DR software is unable to resync the Active-CAJ pair whereas in other cases it re-syncs
Active-CAJ pair automatically. 3DC DR software logs appropriate messages in the package
configuration file and sends the notification to the user if DGM is configured. The user has to
manually resync the Active-CAJ pair in this scenario.
During the failover of a package from DC1 to DC2, the Delta Resync pair is re-synchronized only
when it is not able to replicate the data over both DC1-DC2 pair and Active-CAJ pair (i.e. only
when data is not protected at any other site). Only in this scenario, Active-CAJ pair is changed.
For example, the application package is running on DC1 and data is being replicated to DC3
from DC1. Upon entire DC1 failure, the application package fails over to a node in DC2. Since
data cannot be replicated from DC2 to DC1, it is not possible to replicate data to DC3 using the
existing Active-CAJ pair. To replicate data to DC3, the Delta Resync pair between DC2 and DC3
is resynchronized automatically during the package startup. This starts replicating the data from
DC2 to DC3 and the device group between DC2 and DC3 becomes new Active-CAJ pair as shown
in Figure 47 (page 144).
Figure 47 Package Failover upon entire DC1 failure
144 Designing a Three Data Center Disaster Recovery Solution