Large Scale Cluster using dsync and tagged director

Just been reading up on some of dovecot features and was wondering if anyone had played around with large scale systems made up from mutliple small dsync clusters and using tagged director to split users between nodes of a sync'd cluster (rather than nfs).

I know traditionally its been shared storage and multiple nodes and dovecots own doco suggest dsync for several thousands rather than millions but given the cloud seems to be all about replication what about many smaller nodes using dsync and scaling horizontally ?

The only issue is how does director scale when there are serveral(or rather lots of) 'tags' ... in fact what are the limitations with director ?

Matt

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