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

Figure 63 3DC DR Solution Configuration
The 3DC DR Solution consists of three sites: Site1, Site2 and Site3 as shown in Figure 63 (page 414).
There is a P9000 or XP array at each site and they are connected to each other using Continuous
Access links. The nodes and the two XP arrays at Site1 and Site2 are configured as a Metrocluster.
At Site3, an independent Serviceguard cluster is configured and connected to a third P9000 or
XP disk array. A Continentalclusters is configured with the Metrocluster at Site1 and Site2, as the
primary cluster and the independent cluster at Site3 as the recovery cluster.
Overview of Continuous Access 3DC Replication Technology
The Continuos Access 3DC replication can be configured using either 3DC Sync/CAJ replication
or 3DC CAJ/CAJ replication. Here CAJ refers to Continuous Access Journal. In 3DC Sync/CAJ
replication, the replication between the sites located in Metrocluster is synchronous and configured
using Continuous Access Synchronous device group pair where as in 3DC CAJ/CAJ replication,
the replication between the sites located in Metrocluster is asynchronous and configured using
Continuous Access Journal replication device group pair. For information regarding CAJ, see HP
StorageWorks P9000 Continuous Access Journal Software User Guide or HP StorageWorks
XP24000/XP20000 Continuous Access Journal Software User Guide available at http://
h20000.www2.hp.com/bizsupport/TechSupport/Home.jsp.
Table 31 Difference Between 3DC Sync/CAJ and 3DC CAJ/CAJ Replication
3DC CAJ/CAJ replication3DC Sync/CAJ replication
The replication between the sites in a Metrocluster is
asynchronous using Continous Access Journal replication
available in StorageWorks XP and P9000 Storage Arrays.
The replication between the sites in a Metrocluster is
synchronous.
Data may be lagging at the other site in the Metrocluster.Highest level of data currency is maintained at the other
site in the Metrocluster.
Performance of the application is not impacted due to the
replication between the sites in the Metrocluster.
Performance of the application may be impacted due to
the synchronous replication between the sites in the
Metrocluster. This depends on workload, intersite link
bandwidth provisioned and read/write ratio amongst other
factors.
414 Designing a Three Data Center Disaster Recovery Solution