Book Image

PostgreSQL 9 High Availability Cookbook

By : Shaun Thomas
Book Image

PostgreSQL 9 High Availability Cookbook

By: Shaun Thomas

Overview of this book

A comprehensive series of dependable recipes to design, build, and implement a PostgreSQL server architecture free of common pitfalls that can operate for years to come. Each chapter is packed with instructions and examples to simplify even highly complex database operations. If you are a PostgreSQL DBA working on Linux systems who want a database that never gives up, this book is for you. If you've ever experienced a database outage, restored from a backup, spent hours trying to repair a malfunctioning cluster, or simply want to guarantee system stability, this book is definitely for you.
Table of Contents (12 chapters)
11
Index

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 only sorted to the head of the list as long as their I/O continues to limit its long-term usefulness. 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...