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# The Software-RAID HOWTO

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

v1.1, 2004-06-03

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

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