Book Image

Red Hat Enterprise Linux Troubleshooting Guide

By : Benjamin Cane
Book Image

Red Hat Enterprise Linux Troubleshooting Guide

By: Benjamin Cane

Overview of this book

Red Hat Enterprise Linux is an operating system that allows you to modernize your infrastructure, boost efficiency through virtualization, and finally prepare your data center for an open, hybrid cloud IT architecture. It provides the stability to take on today's challenges and the flexibility to adapt to tomorrow's demands. In this book, you begin with simple troubleshooting best practices and get an overview of the Linux commands used for troubleshooting. The book will cover the troubleshooting methods for web applications and services such as Apache and MySQL. Then, you will learn to identify system performance bottlenecks and troubleshoot network issues; all while learning about vital troubleshooting steps such as understanding the problem statement, establishing a hypothesis, and understanding trial, error, and documentation. Next, the book will show you how to capture and analyze network traffic, use advanced system troubleshooting tools such as strace, tcpdump & dmesg, and discover common issues with system defaults. Finally, the book will take you through a detailed root cause analysis of an unexpected reboot where you will learn to recover a downed system.
Table of Contents (19 chapters)
Red Hat Enterprise Linux Troubleshooting Guide
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Back to troubleshooting our RAID


Now that we have a better understanding of RAID and the different configurations, let's go back to investigating our errors.

Apr 26 10:25:44 nfs kernel: md/raid1:md127: Disk failure on sdb1, disabling device.
md/raid1:md127: Operation continuing on 1 devices.

From the preceding error, we can see that our RAID device is md127. We can also see that this device is a RAID 1 device (md/raid1). The message stating Operation continuing on 1 devices means the second part of the mirror is still operational.

The good thing is that, if both sides of the mirror were unavailable, the RAID would completely fail and result in worse issues.

Since we now know the RAID device affected, the type of RAID used, and even the hard disk that failed, we have quite a bit of information about this failure. If we continue looking at the log entries from /var/log/messages, we can find out even more:

Apr 26 10:25:55 nfs kernel: md: unbind<sdb1>
Apr 26 10:25:55 nfs kernel: md: export_rdev...