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Re: Troubleshooting synchronization

--On Thursday, November 05, 2009 10:06 PM +0100 "Torsten Schlabach (Tascel eG)" <tschlabach@tascel.net> wrote:

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.

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?

Sounds like that is what he meant.

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.

There's a section on this in the admin guide. I think having HA masters is desirable, thus I find Mirror Mode a plus.

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.)

Again, a good argument for 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.

True. But see the section in the admin guide about the issues with MMR. And, as far as the OpenLDAP Development team is concerned, MMR is a fully supported feature. However, there have been issues with it that are being fixed as they are found. It'd be best, for example, to use current RE24 CVS Head, as there's a fix to syncprov in it.



Quanah Gibson-Mount
Principal Software Engineer
Zimbra, Inc
Zimbra ::  the leader in open source messaging and collaboration