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

Tracking I/O-heavy processes with iotop

Many DBAs and system administrators are familiar with the top command, which displays the processes that use the most CPU or RAM. However, this does not help us find the processes that cause high amounts of system I/O.

Fortunately, there is a command, much like top, that is designed specifically for displaying the processes that make storage requests. The iotop utility displays a continuously updated list of the processes and any I/O they are handling. Provided that the server is dedicated to PostgreSQL, we can use this information to almost instantly identify one or more database backends that make disk requests.

Just like top, processes are sorted to the head of the list according to the volume of their I/O. Let's learn more about iotop and see if we can benefit from its functionality.

Getting ready

The iotop command can only be executed by root-level users, as it uses some kernel resources available only to superusers. Be ready with the sudo command...