Designing Disaster Recovery Clusters using Metroclusters and Continentalclusters, Reprinted October 2011 (5900-1881)

• Site 3 is the second-standby site or DC3 for both application A and B.
• The application A is configured using 3DC Sync/CAJ replication. The application B is
configured using 3DC CAJ/CAJ replication.
• For the application A, the data is replicated in a Multi-Target topology from Site 1 to Site 2
and then Site 1 to Site 3. A Delta Resync pair is configured between Site 2 and Site 3.
• For the application B, the data is replicated in a Multi-Target topology from Site 2 to Site 1
and then Site 2 to Site 3. A Delta Resync pair is configured between Site 1 and Site 3.
Figure 76 (page 426) depicts an example of only the applications whose data is being replicated
in a Multi-Target topology. There can also be applications whose data is being replicated in a
Multi-Hop topology.
NOTE: At any point in time, the administrator can change an application’s replication flow to
use different links by interchanging the Delta Resync pair and Active-CAJ pair. For example, if the
replication load is more over the link where Active-CAJ pair is configured, the administrator can
balance the replication load by using a different link to replicate the data to DC3 by interchanging
the Delta Resync pair and Active-CAJ pair. There is no need to change the application’s package
configuration to achieve this.
Bi-Link Configuration
In Bi-Link configuration, for each application, a 3DC replication using two device group pairs is
configured to replicate the data across all its three site as shown in Figure 77 (page 427).
Figure 77 (page 427) depicts an example of Continuous Access link configured between Site1 and
Site3. You can also have Continuous Access link configured between Site2 and Site3 instead of
between Site1 and Site3.
Figure 77 Applications Deployed in a 3DC DR Solution using Bi-Link Configuration
A Continuous Access Synchronous device group pair must be established when using 3DC Sync/CAJ
replication to replicate data between the arrays at the application’s DC1 and DC2 sites. A
Continuous Access Journal device group pair must be established when using 3DC CAJ/CAJ
replication to replicate data between the arrays at the application’s DC1 and DC2 sites. Figure 77
(page 427) depicts both the applications configured using 3DC Sync/CAJ replication and 3DC
CAJ/CAJ replication. You can also have all the applications using only 3DC Sync/CAJ replication
or all the applications using only 3DC CAJ/CAJ replication in a 3DC environment based on your
Overview of 3DC DR Solution 427