Figure 70 Delta Resync Configuration

In a 3DC replication configured with Delta Resync functionality, data is replicated to the third site from one of the sites in the Metrocluster; a Delta Resync pair is configured from the other site. In the event of failure of the site from which data is being copied to the third site, the Delta Resync pair can be used. To replicate data to the third site over Delta Resync pair, run the pairresync command on the Delta Resync pair. This copies only the delta changes providing faster re-synchronization of the data.

For more information on Delta Resync pair, 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.

Remote Command Device

The Remote Command Device (RCMD) feature allows the storage administrator to present the command device from one array to another remote array via the P9000 or XP External Storage functionality. In case of 3DC Tri-Link configuration using Delta Resync, remote command devices must be created on each P9000 or XP array for the other two P9000 or XP arrays. In 3DC replication with Delta Resync, it is required to assign a remote command device to the mirrors in each site. Figure 71 (page 421) shows the Configuration of the Delta resync operation that utilizes RCMD. To configure Remote Command Devices, see section Configuring Delta Resync Operation Environment that uses Remote Command Devices in the document HP StorageWorks P9000 Continuous Access Journal Software User Guide or HP StorageWorks XP24000/XP20000 Continuous Access Journal Software User Guide available at:

420 Designing a Three Data Center Disaster Recovery Solution