I see a significant difference when synchronizing data between Primary - Secondary and between Primary HA and Secondary HA as part of Distributed Availability Groups.
The difference in the amount of data sent across the wire. When making a significant amount of changes on Primary including change tracking enabled tables, we see a huge jump in the amount of data in Redo Queue on all local replicas (synchronous - compression disabled and asynchronous-compression enabled). But across DAG, redo queue is much lower and processing much faster without any significant backlog.
I want to understand on a deeper technical level the difference between local synchronization and DAG.
The specific questions: - What is the difference between synchronizing from Primary to Secondary and across DAG (amount of data) - Can we enable local synchronization to work similar to the one across DAG - What factors that affect the amount of data sent across the wire beside the obvious ones - activity on the DB and HA compression enabled/disabled