replication

[Michael Menge]

Hello,

Quoting Bron Gondwana <brong at fastmail.fm>:

> 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


--------------------------------------------------------------------------------
M.Menge                                Tel.: (49) 7071/29-70316
Universität Tübingen                   Fax.: (49) 7071/29-5912
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