Dell PowerFlex 4.6.x Technical Overview

Replication initial copy

When replication is first activated for a replication consistency group, the target volumes must be synchronized with the source volumes.

For each replication pair, the entire contents of each source volume are copied to the corresponding target volume when replication is active. This occurs when the replication consistency group containing the replication pair is activated, or when the replication pair is added to an already active replication consistency group. When there is more than one replication pair in the replication consistency group, the order in which the volumes are synchronized is determined by the order in which the replication pairs were activated. You can manually override this order, and also pause and resume the initial copy process, using CLI commands.

The initial synchronization is carried out while the applications are running and performing I/O. Any writes to an area of the volume that has already been synchronized will be sent to the journal. Writes to an area of the volume that has not already been synchronized will be ignored, as the updated content will be copied over eventually as part of the synchronization.

The system limits the number of volumes that undergo Initial Copy at any point in time. New volume pairs added to existing replication consistency groups are given priority over new replication consistency groups. This means that replication pairs in a newly activated replication consistency group may not start Initial Copy immediately.