Hi Dieter!
Your answers are very helpful, thanks for that!
directory design, I wonder if I am suffering from a misconception here, i.e. mixing up N-way multi-master and mirror mode possibly.
probably
So looking at
http://www.openldap.org/doc/admin24/replication.html#Configuring%20the%20dif...
What I understand is:
18.3.1. Syncrepl
This is about the syncrepl engine as such. So this is applicable to all types of replication and it's the technical basics, right?
18.3.2. Delta-syncrepl
I guess this is simple master-slave, isn't it? Though I fail to understand why this is about deltas while obviously the other mechanisms aren't, are they?
18.3.3. N-Way Multi-Master
This was the first section which explained something which sounded like what I am looking for. So I went for it.
18.3.4. MirrorMode
Looking at the config example, I just can't tell the difference to 18.3.3. N-Way Multi-Master except:
- samples in this section are not cn=config based, but I guess that shouldn't matter but it's just a question of which mechanism I like to use, isn't it? - in both N-Way Multi-Master and in Mirror Mode I have serverID, mirrormode on and syncrepl statements.
So what actually is the difference between Mirror Mode and N-Way Multi-Master except having 2 servers or three servers?
Regards, Torsten
Dieter Kluenter schrieb:
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: http://www.openldap.org/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?
Yes
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.
probably
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