Book Image

PostgreSQL High Availability Cookbook - Second Edition

By : Shaun Thomas
Book Image

PostgreSQL High Availability Cookbook - Second Edition

By: Shaun Thomas

Overview of this book

Databases are nothing without the data they store. In the event of a failure - catastrophic or otherwise - immediate recovery is essential. By carefully combining multiple servers, it’s even possible to hide the fact a failure occurred at all. From hardware selection to software stacks and horizontal scalability, this book will help you build a versatile PostgreSQL cluster that will survive crashes, resist data corruption, and grow smoothly with customer demand. It all begins with hardware selection for the skeleton of an efficient PostgreSQL database cluster. Then it’s on to preventing downtime as well as troubleshooting some real life problems that administrators commonly face. Next, we add database monitoring to the stack, using collectd, Nagios, and Graphite. And no stack is complete without replication using multiple internal and external tools, including the newly released pglogical extension. Pacemaker or Raft consensus tools are the final piece to grant the cluster the ability to heal itself. We even round off by tackling the complex problem of data scalability. This book exploits many new features introduced in PostgreSQL 9.6 to make the database more efficient and adaptive, and most importantly, keep it running.
Table of Contents (18 chapters)
Title Page
About the Author
About the Reviewer
Customer Feedback

Evaluating the current disk performance with iostat

Due to the disparity in speed between storage and RAM, one of the first signs of distress that a DBA will observe is directly related to disk utilization. A badly written query, an unexpected batch-loading process, a forced checkpoint, overwhelmed write caches - the array of things that can ruin disk performance is vast.

The first step in tracking down the culprit(s) is to visualize the activity. The iostat utility is fairly coarse in that it does not operate at the process level. However, it does output storage activity by device and includes columns such as reads or writes per second, the size of the request queue, and how busy it is compared to its maximum throughput.

This allows us to see the devices that are actually slow, busy, or overworked. Furthermore, we can combine this information with other methods of analysis to find the activity's source. For now, let's explore the tool itself.

Getting ready

As iostat is part of the sysstat package...