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

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 number 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...