Mirror-mode is active/passive-fail-over.

The load balancer should be configured to direct traffic to one of them, switching to the other only when the first is down.

- chris

Chris Jacobs Systems Administrator, Technology Services Group

Apollo Group | Apollo Marketing & Product Development | Aptimus, Inc. 1501 4th Ave | Suite 2500 | Seattle, WA 98101 direct 206.839.8245 | cell 206.601.3256 | Fax 206.644.0628 email: chris.jacobs@apollogrp.edu

----- Original Message ----- From: openldap-technical-bounces@OpenLDAP.org openldap-technical-bounces@OpenLDAP.org To: openldap-technical@openldap.org openldap-technical@openldap.org Sent: Wed Sep 05 02:00:26 2012 Subject: Slaving from Mirror Mode

Dear Folks,

I am having trouble understanding http://www.openldap.org/doc/admin24/dual_dc.png. In particular, I do not understand the exact meaning of the bidirectional arrows, and the purpose of the upper pair of load balancers.

1, Are the upper load balancers there to chain writes to both mirror mode masters?

2. Are the "replica pool" configured to replicate from both masters or only from one?

I am setting up mirror mode masters both in the same data centre, with one slave offsite. Should all the slaves slave from both masters, or should they slave from a load balancer which decides which master is getting the writes at present?

Although our slaves are busy, surviving network issues with data consistent and correct is very important. Network outages and strange disconnects are the rule without automated configuration management for network devices. -- Nick Urbanik http://nicku.org 808-71011 nick.urbanik@optusnet.com.au GPG: 7FFA CDC7 5A77 0558 DC7A 790A 16DF EC5B BB9D 2C24 ID: BB9D2C24 I disclaim, therefore I am.

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Dear Quanah,

On 05/09/12 10:06 -0700, Quanah Gibson-Mount wrote:

--On Wednesday, September 05, 2012 7:00 PM +1000 Nick Urbanik nick.urbanik@optusnet.com.au wrote:

...

I am setting up mirror mode masters both in the same data centre, with one slave offsite. Should all the slaves slave from both masters, or should they slave from a load balancer which decides which master is getting the writes at present?

I'm never sure what you mean when you say the replica's should slave from both masters. A replica can only take updates from *one* master for a given tree. Your best option in your case is to set up MMR where only one master is taking writes (mirror mode), and have the replica use a load balanced name between the two masters as its "master" for updates. That should keep data consistent.

So you mean that all the slaves should slave through the load balancer, as well as writes go through the load balancer?

I was going to set up the masters so that writes would go through the load balancer, but slaves read from both masters like the multi-master example shown at http://www.openldap.org/doc/admin24/replication.html#N-Way%20Multi-Master

Thanks for that.

USE OF DELTA-SYNCREPL FROM MIRROR-MODE MASTER TO CONSUMERS ==========================================================

I have another question relating to section "18.3.4.1.2. Normal Consumer Configuration" where there is this text:

This is exactly the same as the Set up the consumer slapd section. It can either setup in normal syncrepl replication mode, or in delta-syncrepl replication mode.

So while I cannot use delta-syncrepl *between* the two mirror-mode masters, I *can* use delta-syncrepl on our eight consumers slaving *from* the current active master through the load balancer? Is that correct?

The eight consumers are what our clients read from.

Dear Quanah,

On 05/09/12 13:52 -0700, Quanah Gibson-Mount wrote:

--On Thursday, September 06, 2012 6:46 AM +1000 Nick Urbanik nicku@nicku.org wrote:

...

So while I cannot use delta-syncrepl *between* the two mirror-mode masters, I *can* use delta-syncrepl on our eight consumers slaving *from* the current active master through the load balancer? Is that correct?

No. OpenLDAP 2.4.32 has full delta-syncrepl MMR support. ;) So you can use delta-syncrepl everywhere. 18.3.4.1.2 is specifically talking about a replica replicating from only a single master, not from multiple masters (as in a load balance name). Basically what you are looking at is 18.3.4.1.1.

Now MMR is not mirror mode replication, but multi-master replication, correct?

Now we're going to use a pair of mirror mode masters, and there must be only syncrepl between them, not delta-synrepl between them, correct? Or do you mean that you can use delta-syncrepl between the mirror mode masters as well? I'm confused by your statement, "you can use delta-syncrepl everywhere."

But it *is* possible to use delta-syncrepl from the current active mirror master to all the non-master consumers, is that correct?

I really appreciate your generous patience!