Hello everyone,

I recently noticed in the OpenLDAP section of the Ubuntu Server Guide
that we suggest people configure replication in multi-master mode (MMR).
I respectfully disagree with that, and would like to discuss whether we
should document single-master replication instead.

Smarter people that I have argued[1] against MMR through and thorough.
While MMR can prove useful in certain circumstance (ie, HA), it is not
generally useful and can even lead to unforeseen problems. Plus, the
standard directory model of single-master replication scales better.

So, is there a good reason why we should continue to document (and
hence, implicitly recommend) MMR first and foremost?


[1]: http://tools.ietf.org/html/draft-zeilenga-ldup-harmful-02


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Etienne Goyer
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Etienne Goyer wrote:
> Smarter people that I have argued[1] against MMR ...

That really should have read: "Smarter people *than* I ...". Otherwise,
the sense is completely warped.

Damn caffeine makes me dyslexic.


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I think the documentation should cover both configurations and let the reader decide which to pursue. *While MMR involving more than two systems can become complicated and may cause obscure problems especially for new users, MMR on two systems works quite well with a fairly simple configuration and tends reduce complexity of methods used to provide redundancy (e.g., Linux-HA).


On Wed, Jan 13, 2010 at 12:51 PM, Etienne Goyer <etienne.goyer@canonical.com> wrote:

Etienne Goyer wrote:

> Smarter people that I have argued[1] against MMR ...



That really should have read: "Smarter people *than* I ...". *Otherwise,

the sense is completely warped. *



Damn caffeine makes me dyslexic.





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Etienne Goyer

Technical Account Manager - Canonical Ltd

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Matt Kassawara wrote:
> MMR on two systems works quite well with a fairly simple
> configuration and tends reduce complexity of methods used to provide
> redundancy (e.g., Linux-HA).

This is where I disagree: I do not think MMR is useful for the common
scenario, and actually has drawbacks (and, yes, add complexity too). I
am not *against* documenting MMR, but we should steer users toward the
standard directory model first and foremost.

HA is a completely different topic, and not one the guide try to address
in that section. At least, not in its current form.


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Etienne Goyer
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Hello,

On Wed, Jan 13, 2010 at 3:20 PM, Etienne Goyer <etienne.goyer@canonical.com> wrote:




This is where I disagree: I do not think MMR is useful for the common

scenario, and actually has drawbacks (and, yes, add complexity too). *I

am not *against* documenting MMR, but we should steer users toward the

standard directory model first and foremost.



HA is a completely different topic, and not one the guide try to address

in that section. *At least, not in its current form.





I agree with you Etienne, and it's on my TODO list to update the OpenLDAP section with instructions for a master/slave replication setup.* Also, I believe there is a somewhat recent bug suggesting just that.



We could move, after improving if needed, the MMR instructions to the wiki to help those that prefer that setup.* I'm not sure how much time I'll have to work on it this week, but any* and all patches are very welcome :-).



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Hello,
I've changed the Server Guide to use a Single-Master replication method. *You can see the draft version here:
**http://doc.ubuntu.com/ubuntu/serverguide/C/openldap-server.html


All feedback is greatly appreciated. *
The TLS Replication instructions still need to be adjusted, but I should be able to get to that today.


Thanks.
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Adam


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