Book Image

High Availability MySQL Cookbook

By : Alexander Davies
Book Image

High Availability MySQL Cookbook

By: Alexander Davies

Overview of this book

High Availability is something that all web sites hope to achieve, especially those that are linked to big companies.MySQL, an open source relational database management system (RDBMS), can be made highly available to protect from corruption, hardware failure, software crashes, and user error. Running a MySQL setup is quite simple. Things start getting complex when you start thinking about the best way to provide redundancy. There are a large number of techniques available to add 'redundancy' and 'high availability' to MySQL, but most are both poorly understood and documented.This book will provide you with recipes showing how to design, implement, and manage a MySQL Cluster and achieve high availability using MySQL replication, block level replication, shared storage, and the open source Global File System (GFS).This book covers all the major techniques available for increasing availability of your MySQL databases. It demonstrates how to design, implement, troubleshoot and manage a highly available MySQL setup using any one of several techniques, which are shown in different recipes. It is based on MySQL Cluster 7.0, MySQL (for non clustered recipes) 5.0.77, and CentOS / RedHat Enterprise Linux 5.3.The book starts by introducing MySQL Cluster as a technology and explaining how to set up a simple cluster. It will help you to master the options available for backing up and restoring a file in the MySQL Cluster. By following the practical examples in this book, you will learn how to manage the MySQL Cluster. Further, we will discuss some troubleshooting aspects of the MySQL Cluster.We also have a look at achieving high availability for MySQL databases with the techniques of MySQL Replication, block level replication, shared storage (a SAN or NAS), and DRBD.Finally, you will learn the principles of Performance tuning and tune MySQL database for optimal performance.
Table of Contents (17 chapters)
High Availability MySQL Cookbook
Credits
About the Author
About the Reviewers
Preface
Base Installation
Index

Fencing for high availability


Fencing, sometimes known as Shoot The Other Node In The Head (STONITH) sounds pretty dramatic, and at first sight it may seem odd that it is a good thing for high availability. In this recipe, we will discuss why fencing is required in all clusters, and then discuss its implementation using the scripts provided with RHEL and CentOS.

There is only one way to be sure that something is dead—that is, to kill it yourself. For a shared-storage cluster, it is considered good enough to ask something to die—but only if it is able to confirm with absolute clarity that it has indeed successfully died. The reason for this caution is that if a node is considered dead, but is in fact able to consider writing to a shared-storage device (as may occur in the case of a kernel bug for example), the consequences may be total data loss on the shared-storage volume.

What this means in practical terms with shared-storage clusters is that in the event of a controlled movement of a service...