Delta resync configuration

With the delta resync configuration, you bring the S-VOL to a consistent state more quickly after failure because only missing differential data must be copied.

You can set up two secondary sites for one primary site. Install at least one VSP F800, VSP G800, VSP F1500, or VSP G1x00 at the primary site, the intermediate site, and the secondary site respectively.

Copying data between two secondary sites in the event of a failure or disaster at the primary site is called delta resync. In a 3DC multi-target configuration using delta resync, only the differential data lost by a primary site failure is copied from the TC secondary site to the UR secondary site. As a result, data at a secondary site in a remote location can be restored more quickly.

You create the delta resync configuration by adding a second UR pair to the 3DC multi-target configuration, using the TC S-VOL and the UR S-VOL, as illustrated in the following figure. The delta resync operation is performed when the primary site fails.

Parent Topic

• Configurations with TrueCopy

Child Topics

• Additional task for the 3DC multi-target configuration using delta resync

  To use delta resync, you need to perform an additional task after setting up 3DC multi-target configuration.

• Creating the delta resync pair
• Setting up remote command devices for use with RAID Manager
• Mapping remote command devices for delta resync operations
• Assigning mirrors to remote command devices for delta resync operations

  You assign the mirror IDs used by the configuration’s journals to the remote command devices. This enables UR control information regarding the delta resync to be transferred and then read at the secondary sites. This is necessary for the delta resync operation.

• Releasing a remote command device for delta resync operations assigned to a mirror
• Relationship between deleted associated pairs and assigned remote command devices

  You can change a 3DC configuration that uses the delta resync function to a configuration that does not use it by deleting pairs. At this time, along with the deleted pairs, associated pairs are also deleted automatically, and the assignment of remote command devices is released automatically.

• Performing the delta resync operation