Hi,
if you have only one pair of servers, I think replication via dovecot's dsync (or doveadm via ssh) where each server holds all emails as a local storage would be easiest.
There is a caveat with shared folders though. And dovecot replicates only emails. The index is not included, which means for example that you'd need 2 databases for quota - otherwise emails would count twice. Well and any manual index management needs to be done on both sides.
https://wiki.dovecot.org/Replication
Running a cluster filesystem or NFS as a common base is possible but needs some adjustments of dovecot like turning off caching or memory mapping, which in turn decrease performance.
This is only some short handbook knowledge as I haven't implemented replication yet.
Greetings Martin Johannes Dauser
On Mon, 2018-11-19 at 17:51 -0800, Daniel Miller wrote:
I have a small but critical server that supports our group. As a single server - it's obviously a single-point-of-failure for lots of things. As I just experienced...again. It was a lot more fun building systems from components when I was younger...
Previously 3rd-party hosted solutions didn't look attractive for several reasons...but I'm seeing prices now for cloud virtual machines that are stupid cheap. Even if they wind up being limited speed & availability - it would seem they'd be a lot better than nothing!
So I'm considering having at least one backup server for various services - obviously that includes mail. So now I have to wonder about the backend. And while I think I'm reasonably current with networked file systems (not distributed or cluster) I haven't played with replication for a quite a while.
For this particular usage (I'm envisioning two servers total) - is there a need/reason to use any form of networked/distributed/cluster file storage? Or would this be accomplished via "pure" Dovecot - dsync replication would keep things updated between the servers and director would handle the connections? So with identically configured SMTP servers, passing to the local LMTP agents, the file system would be "purely local" with no NFS or other interconnection?