HP XP P9500 Storage - Manual (Page 149)

The delta resync operation requires less time to bring the S-VOL to a consistent state after a failure
occurs because only missing differential data is copied. The delta resync operation is performed
when the primary site fails, as illustrated in the figure below.
In addition, you can create or re-create the Cnt Ac-J Z pair for delta resync:
•
When the Cnt Ac-J Z pair status changes to HOLD after the delta resync operation.
•
When you re-create the Cnt Ac-J Z pair for delta resync when recovering the primary site.
Figure 22 3DC multi-target with delta resync
Two operations are performed for the delta resync configuration:
•
Create the Cnt Ac-J Z delta resync pair
•
In a disaster recovery situation, perform the delta resync operation
The delta resync system is created after setting up the main Cnt Ac-S Z and Cnt Ac-J Z pairs in the
multi-target configuration.
•
Data is not copied at the time you set up the delta resync pair. The primary volume (P-VOL)
and S-VOL in this system contain data from their respective Cnt Ac-S Z and Cnt Ac-J Z systems
•
If a failure on the primary site occurs, the Cnt Ac-S Z S-VOL is made the primary production
volume using Business Continuity Manager commands. Differential data stored in the journal
volumes is used to synchronize the S-VOL, via the pairresync operation.
Figure 23 Delta resync in a primary site disaster
Delta resync configuration 149