Multi-server but small scale

Martin Johannes Dauser
2018-11-21T07:52:51Z

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?
>