Hello, thanks for your answer.
At the time of the issue:
- between 2 and 30 mbits/s using mongod synchronization
- 120 mbits/s using rsync/scp
Finally, I was able to stabilize the cluster but not using mongod:
- I had a full backup of the machine which was still in the oplog
- I restored it
- Mongod was able to resync (~ 20 Go) from this point.
Then I added another replica that syncs normally (80 mbit/s) for several hours.
Now I have the production “stable” and started to test the migration to newer versions.