I've got two NAS-R3 servers, same setup.

How to replicate both servers?
I created a volume of 350GB, snapshot 64GB

Shares have data replication enabled.
Created a data replication task under Maintenance -> Backup.
With a interval of 10 minutes ( why not continues synchronization? ).
In the tasks list the replication shows no problems.

When I place a new file on one of the shares sometimes it's replicated, sometimes removed..
Maybe problems with snapshot?