replication

On Tuesday, September 4, 2012 the next DOAG SIG MySQL meeting will take place in Hamburg (Germany) with the topic Replication.

Possible presentations are: MySQL Replication, Galera Cluster, Replication with Oracle GoldenGate, Replication with Zimory Scale and Tungsten Replicator.

The event will presumably be located at the Hotel Böttcherhof at Wöhlerstrasse 2.

Introduction

Galera is a synchronous Multi-Master Replication for MySQL. It is therefore in competition with several other MySQL architectures:

Introduction

MySQL/Galera synchronous Multi-Master Replication consists of 2 parts:

A customer rose a support case with a problem on his Master-Master set-up. The 2^nd Master claims to have a problem:

Vor ein paar Tagen hatte ich wieder einmal mit einer MySQL Cluster Replikation zu tun. Ich habe das schon eine Weile nicht mehr angelangt und war somit vorbereitet, wieder einmal ein paar Überraschungen zu erleben.

Diejenige, für welche MySQL Cluster - Cluster Ring-Replikationen das tägliche Brot ist, können diesen Artikel getrost überspringen. Alle anderen können möglicherweise von unseren Erfahrungen profitieren.

Wir hatten das folgende MySQL Cluster Konstrukt im Einsatz:

A few days ago I had to deal with MySQL Cluster replication. I did not do this for a while so I was prepared to expect some interesting surprises once again.

For those who MySQL Cluster - Cluster circular replication is the daily business they may skip this article. For all the others they possibly can profit from our learnings.

I am talking about the following MySQL Cluster set-up:

Introduction

One of the features that make MySQL so great is its easy replication set-up. If you are experienced and know-how to do it, it takes you about 15 minutes to set-up a slave. What you have in the end is a replication from one master to one or several slaves. So you can build a top-down data stream pyramid and spread your data on many slaves.

Electing a slave as new master and aligning the other slaves to the new master

In a simple MySQL Replication set-up you have high-availability (HA) on the read side (r). But for the master which covers all the writes (w) and the time critical read (rt) there is no HA implemented. For some situations this can be OK. For example if you have rarely writes or if you can wait until a new Master is set up.

But in other cases you need a fast failover to a new master.

According to Johans wishes I write down my concerns about MySQL (Cluster) replication. These items are things I run again and again into it with customers:

MySQL provides its replication for High Availability (HA) and for read Scale-out. Generally it is known that in a MySQL replication you can only replicate from one Master to many slaves. In this paper it is shown how a set-up can look like to replicate from two masters to one slave.

Caution: Handle this information with care!!!