Hi
Looking for some guidance on how to setup a dovecot cluster with more than 2 servers. Ideally as multiple masters so I don't have the complexity of back recovery/synchronisation in failover situations. And I can utilised upstream load balancers (director or other) to automatically move between available nodes.
Current pattern is: High availability at one site (AWS availability zone) with two active servers behind dovecot directors and an AWS network load balancer in front of the directors.
A third dovecot server as a disaster recovery instance (another availability zone or region), with ideally real time and bidirectional replication. Behind a different network and NLB access path. Dovecot --version = 2.3.14 Centos 7
Previously for the HA pair we utilised NFS but the AWS EFS equivalent doesn't perform ( very high latency and NFS meta data caching required). And then for DR we utilised the dovecot replication. 2 way so I have automated recovery and could do active active testing/verification as required with no down time. This help verify recovery pathways.
https://doc.dovecot.org/configuration_manual/replication/# - reading the documentation is seems clear that replication only supports a PAIR of masters. Any ideas on how I can add in a 3rd replication node? Two pairs? I'm happy to utilise a star pattern. HA 1 <-> HA2, HA 1 <-> DR.
Not possible? Can I run more than one replicator? Or should I utilise doveadm sync via cron jobs and 2-way sync.
Any thoughts, suggestions most welcome. How are others achieving > 2 clusters for dovecot servers supporting the same domain? Most of this is for availability rather than purely performance scaling.
Thanks Raymond