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Red Hat Enterprise Linux Troubleshooting Guide

You're reading from   Red Hat Enterprise Linux Troubleshooting Guide Identify, capture and resolve common issues faced by Red Hat Enterprise Linux administrators using best practices and advanced troubleshooting techniques

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Product type Paperback
Published in Oct 2015
Publisher
ISBN-13 9781785283550
Length 458 pages
Edition 1st Edition
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Author (1):
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Benjamin Cane Benjamin Cane
Author Profile Icon Benjamin Cane
Benjamin Cane
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Table of Contents (14) Chapters Close

Preface 1. Troubleshooting Best Practices FREE CHAPTER 2. Troubleshooting Commands and Sources of Useful Information 3. Troubleshooting a Web Application 4. Troubleshooting Performance Issues 5. Network Troubleshooting 6. Diagnosing and Correcting Firewall Issues 7. Filesystem Errors and Recovery 8. Hardware Troubleshooting 9. Using System Tools to Troubleshoot Applications 10. Understanding Linux User and Kernel Limits 11. Recovering from Common Failures 12. Root Cause Analysis of an Unexpected Reboot Index

Identifying a bigger issue


Earlier while using mdadm to look at the current status of md127, we could see that the RAID device md127 had a disk removed from service. While looking through /proc/mdstat we discovered that there is another RAID device /dev/md126, and that too has a disk removed from service.

Another interesting item that we can see is that the RAID device /dev/md126 is a surviving disk: /dev/sda1. This is interesting because the surviving disk for /dev/md127 is /dev/sda2. If we remember from the earlier chapter /dev/sda1 and /dev/sda2 are simply 2 partitions from the same physical disk. Given the fact that both RAID devices have a missing drive and that our logs state that /dev/md127 had /dev/sdb1 removed and re-added. It is likely that both /dev/md127 and /dev/md126 are using partitions from /dev/sdb.

Since /proc/mdstat only has two statuses for RAID devices, up or down, we can confirm whether the second disk has actually been removed from /dev/md126 using the --detail flag...

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