MMR has supported delta-syncrepl since 2.4.27.  You should use it.

I did consider delta-syncrepl, but given the high write load expected, I  was not sure if it was the right decision. I am expecting an average  load of 50-100 writes per second, and with 1 backup provider, and 10  consumers, it might get heavy on the provider which is serving the  writes, given that OpenLDAP would be maintaining another DB for the  access log.

But with this syncrepl issue, it looks like I need to change the  replication mode to refreshAndPersist anyway. As such it looks like  delta syncrepl is also refreshAndPersist too.

Is there any recommendation between simple refreshAndPersist and  delta-syncrepl with refreshAndPersist for high write loads?

Thanks

PS: I see that delta syncrepl is compatible with MMR which I presume  to be MultiMaster. I hope it works with Mirror Mode too. I did not find  any documents supporting this.