Re: replication

Michael Menge <michael.menge@xxxxxxxxxxxxxxxxxxxx> · Fri, 12 Nov 2010 22:36:44 +0100

Hello,

Quoting Bron Gondwana <brong@xxxxxxxxxxx>:

On Fri, Nov 12, 2010 at 02:02:01PM -0500, Ron Vachiyer wrote:

Hello,

I am currently investigating the possibility of adding a second  
cyrus server, the goal being to entirely duplicate the  
mailspool/userbase and have users POP in some sort of balanced  
means, either DNS load balancing or otherwise.  We have a pool of  
inbound MX servers that handle email, delivering to Cyrus over  
lmtp.  In the event of a crash, we would want to repair/rebuild the  
dead server and have it re-join the pairing.

I have read on this list's archives that having user interaction on  
two replicated servers is iffy, and I wonder what the point is, or  
is there alternative documentation/methods I should be considering  
to do this.  If it is true that popping email off of two servers  
set up in replication is a bad idea, I wonder what the point of it  
really is?

It's getting better, but it's still not 100% reliable to have
master/master replication between two servers with interactions
going to both sides.

It SHOULD be safe now to have a single master/master setup with
individual users on one side or the other - but note that nobody
is known to be running that setup successfully yet.

As for what the point is?  I don't know about you, but I run a
24hr/day shop, and I like to be able to take a server down for
maintainence in about 2 minutes, with users seeing a brief
disconnection and then being able to keep using the service
with minimal disruption.

Bron.

As Bron already mentioned the problems of master/master mode
you can easy live without.

We run multiple servers, these are paired, each server is running one
cyrus instance in as master and one as slave, so that the pairs
replicate each other. In case of a crash one server would run two  
master instances.

You only need a way of splitting the users between the  servers.
That could be DNS, a proxy or murder setup.

Regards

      Michael Menge

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