Introduction

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

Galera features

Galera provides the following features:

• Synchronous replication
• Active/active multi-master topology
• Read and write to any cluster node
• Automatic membership control, failed nodes drop from the cluster
• Automatic node joining
• True parallel row level replication
• Direct client connections
• Drop-in replacement for native MySQL

Galera benefits

Benefits using Galera Replication:

• High Availability
• No slave lag

In the following article I have summarized some steps and hints to set-up a MySQL active/passive fail-over Cluster also sometimes called MySQL HA.

With such a set-up you can achieve a 99.99% (4x9) HA set-up for MySQL (52 minutes downtime per year). The same procedure also works for PostgreSQL, Oracle and other database systems running on Linux (DRBD runs on Linux only).

The concept

The concept of an active/passive fail-over Cluster is the following:

The FromDual Performance Monitor for MySQL has now a new module for monitoring DRBD. Since more an more of our customers want to run MySQL High Availability solutions based on DRBD we have implemented this module.

We gather all information which are reported with the command:

The following solutions are used with MySQL:

We have had the following presentations:

When I set-up a MySQL HA environment for customers I usually do some final fail over tests after configuring the whole beast.

To check if the application behaves like expected I always run my little test application (test.sh) from the server(s) where the customers application runs.

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.