Ha

After properly installing and testing a Galera Cluster we see that the set-up is not finished yet. It needs something in front of the Galera Cluster that balances the load over all nodes.
So we install a load balancer in front of the Galera Cluster. Typically nowadays HAProxy is chosen for this purpose. But then we find, that the whole Galera Cluster is still not high available in case the load balancer fails or dies. So we need a second load balancer for high availability.
But how should we properly …

Introduction

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

• Master-Master Replication with MySQL
• MySQL Cluster
• The non-open source product called Schooner

Very often they can be easily replaced by Galera’s synchronous Multi-Master Replication for MySQL.

All those products have some advantages and disadvantages. Very often MySQL Master-Master Replication is used in the field because of its simplicity to set-up. But …

In the following article I have summarized some steps and hints to set-up a MySQL active/passive failover 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 failover Cluster is the following:

• You have 2 servers (also called nodes).
• They communicate …

The following solutions are used with MySQL:

• Redhat Cluster Suite (RHCS)
• SteelEye LiefKeeper
• Heartbeat (from the Linux HA project), Using Linux HA Heartbeat
• Crossroads
• Failover
• DRBD, Using MySQL with DRBD
• MySQL Cluster

The following presentations are available:

When I set-up a MySQL HA environment for customers I usually do some final failover 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. It displays “graphically” how the application behaves and you can show to the customer immediately what is going on…

Make sure, that you point it to the virtual IP (VIP) or the load balancer (LB).

It was really …