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High Availability

All High Availability (HA) related stuff.

Unbreakable MySQL Cluster with Galera and Linux Virtual Server (LVS)

Recently we had to set-up a 3-node Galera Cluster with a Load Balancer in front of it. Because Galera Cluster nodes (mysqld) still reply to TCP requests on port 3306 when they are expelled from the Cluster it is not sufficient to just leave it to the Load Balancer to check the port if a Galera node is properly running or not.

Schulungstermine für MySQL Kurse 2013 in Deutschland

FromDual bietet auch im Jahr 2013 wieder intensive MySQL Schulungen für fortgeschrittene MySQL Anwender an.

Folgende deutschsprachigen Kurse sind geplant:

Artikel über MySQL im neuen iX

Hallo MySQL Gemeinde,

Im neuen iX (2012-10) hat es zwei nette Artikel über: MySQL HA-Lösungen (S. 116) und MySQL 5.6 (S. 66).

Viel Spass beim Lesen!

SchoonerSQL

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There is a product out in the wild which is called SchoonerSQL [ 1 ] from an American company called Schooner Information Technology [ 2 ].

Codership partners with FromDual to offer consulting and support services for Galera Cluster for MySQL

Helsinki, Finland, Uster, Switzerland – February 18, 2012 – Codership, the provider of Galera Cluster for MySQL, and FromDual, a MySQL consulting company, today announced collaboration to offer Galera Cluster technology and related support and consulting services for Galera users all over the world, especially in German speaking countries Germany, Austria and Switzerland (DACH). Galera Cluster is a synchronous, true multi-master replication cluster for MySQL using the well known InnoDB storage engine.

Galera - Synchronous Multi-Master Replication Cluster for MySQL/InnoDB

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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:

MySQL HA (high availability) Cluster cookbook

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:

MySQL Performance Monitor with DRBD monitoring capabilities

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:

Test application for MySQL high availability (HA) set-up

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. 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).

Active/active fail over cluster with MySQL Replication

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 fail-over to a new master.

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