Removing and re-adding a replica set member

[Stennie_X (Stennie)]

Welcome to the community @Oscar_A!

@Oscar_A

My question is if I remove a member (secondary in site 2) from the replica set, break the comms between site A and B and then write data to the secondary database in site B, then re-add the member to the replica set to be replicated from the primary database in site A, would there be any data corruption?

All members of a replica set share a common write history.

You can remove a member from a replica set and use that in standalone mode or as the seed for another replica set, but that creates a divergent write history. You cannot re-add that member to the original replica set without re-syncing or rolling back the writes (which would undo your goal of writing data to this member).

If you want to merge data back into a single replica set, you will have to backup and restore the relevant data. Merging may be difficult if you have updated the same collections (or documents!) in different deployments.

Regards,
Stennie