The Software-RAID HOWTO

Jakob Østergaard jakob@unthought.net and Emilio Bueso bueso@vives.org

This HOWTO describes how to use Software RAID under Linux. It addresses a specific version of the Software RAID layer, namely the 0.90 RAID layer made by Ingo Molnar and others. This is the RAID layer that is the standard in Linux-2.4, and it is the version that is also used by Linux-2.2 kernels shipped from some vendors. The 0.90 RAID support is available as patches to Linux-2.0 and Linux-2.2, and is by many considered far more stable that the older RAID support already in those kernels.

1. Introduction

• 1.1 Disclaimer
• 1.2 What is RAID?
• 1.3 Terms
• 1.4 The RAID levels
• 1.5 Requirements

2. Why RAID?

• 2.1 Device and filesystem support
• 2.2 Performance
• 2.3 Swapping on RAID
• 2.4 Why mdadm?

3. Devices

• 3.1 Spare disks
• 3.2 Faulty disks

4. Hardware issues

• 4.1 IDE Configuration
• 4.2 Hot Swap

5. RAID setup

• 5.1 General setup
• 5.2 Downloading and installing the RAID tools
• 5.3 Downloading and installing mdadm
• 5.4 Linear mode
• 5.5 RAID-0
• 5.6 RAID-1
• 5.7 RAID-4
• 5.8 RAID-5
• 5.9 The Persistent Superblock
• 5.10 Chunk sizes
• 5.11 Options for mke2fs

6. Detecting, querying and testing

• 6.1 Detecting a drive failure
• 6.2 Querying the arrays status
• 6.3 Simulating a drive failure
• 6.4 Simulating data corruption
• 6.5 Monitoring RAID arrays

7. Tweaking, tuning and troubleshooting

• 7.1 raid-level and raidtab
• 7.2 Autodetection
• 7.3 Booting on RAID
• 7.4 Root filesystem on RAID
• 7.5 Making the system boot on RAID
• 7.6 Converting a non-RAID RedHat System to run on Software RAID
• 7.7 Sharing spare disks between different arrays
• 7.8 Pitfalls

8. Reconstruction

• 8.1 Recovery from a multiple disk failure

9. Performance

• 9.1 RAID-0
• 9.2 RAID-0 with TCQ
• 9.3 RAID-5
• 9.4 RAID-10
• 9.5 Fresh benchmarking tools

10. Related tools

• 10.1 RAID resizing and conversion
• 10.2 Backup

11. Partitioning RAID / LVM on RAID

• 11.1 Partitioning RAID devices
• 11.2 LVM on RAID

12. Credits

13. Changelog

• 13.1 Version 1.1