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Re: Troubleshooting synchronization

Hi Torsten!

"Torsten Schlabach (Tascel eG)" <tschlabach@tascel.net> writes:

> Hi Dieter!
>> The answer is quite simple: do not use multimaster replication in a
>> production environment. In most cases the requirement for multimaster
>> replication is just based on poor directory design.
> If this is a "do not use feature", for what reason has it been included
> in the software, in the first place.

Well, there is the protocol RFC 4510 and the OpenLDAP Project is
aiming to be the reference implementation of this protocol, on the
other hand is the OpenLDAP Project a community driven project:
that is, features not being part of the protocol but may be of
interest to the community, can be included.
With regard to multimaster replication, this feature has only been
included since 2.3 (if I remember correctly) and has undergone heavy
recoding ever since. I personally consider multimaster replication
still as beta and not stable for production use.

>> Slapd in a synchronized environment is, with a few exceptions which
>> have only been fixed recently, rock stable, I know of environments
>> with up to 150 consumers.
> When you say "synchronized", do you mean one master and n slaves?

> When you say, the requirement for N-way multi-master is usually poor
> directory design, I wonder if I am suffering from a misconception here,
> i.e. mixing up N-way multi-master and mirror mode possibly.

> What we want to achieve is a HA solution where *all* directory data is
> stored on more than one physical machine. I know I can do that by having
> a master and a slave. But then I would need to have a mechanism entirely
> external to slapd that if the master fails I turn the slave into a
> master and vice versa. (However this could be reliably achieved.)

What you describe is Mirror Mode.

> So the idea for N-way multi-master was just: I can point the DNS entry
> to whatever server in my cluster (possibly there may be more than two)
> and it will be a writeable directory and I won't ever loose any
> information I write into that LDAP cloud.

OK, this requirement does not include multimaster replication, but
only Mirror Mode of a HA cluster of providers and chaining write
operations of consumers to the active provider.


Dieter Klünter | Systemberatung