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Date: Thu, 24 Feb 2005 00:21:28 -0500
From: "Alan D. Cabrera" <adc@toolazydogs.com>
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To: Apache Directory Developers List <directory-dev@incubator.apache.org>
Subject: Re: [replication] Master slave replication will not suffice
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Alex Karasulu wrote:

>
> I was thinking about replication earlier today.  I was hoping we can 
> quickly implement master slave replication by piggy backing on a JMS 
> implementation like ActiveMQ.  It quickly occured to me however that 
> there is no way we can utilize a master slave rep. configuration 
> without loosing all the benefits of having embedded services like 
> Kerberos, DNS, DHCP etc.
>
> The reasoning behind this has to do with the way master-slave rep. 
> works.  Basically there is one master and all other servers are slaves 
> a.k.a. replicas.  A request to modify a replica returns an error 
> indicating the replica is not writable along with a referral to the 
> master.  I forget the exact LDAP result code returned.  The client 
> would then contact the master for the alteration what ever it may be.  
> The master makes the change and propagates it to the replicas usually 
> using a special replication user that bypasses certain checks.
>
> Here's the problem: with a master slave setup an embedded inet service 
> like Kerberos will have to contact the master of the system to make 
> alterations on all replicas for any alterations to the DIT!  This 
> defeats the entire purpose of embedding the service in the first place 
> and limits the HA yeild from replication.
>
> So what we need is multimaster replication.  This is an order of 
> magnitude more complex than master slave replication. 

Once you have replication what's the point in embedding?


Regards,
Alan