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

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