From HostThyself

This Guide introduces the installation of RAID on CentOS using the text based install.

Description in ths guide is based on the following configuration.

• CentOS 4.4
• Pentium 4
• 2 identical harddisk connected to primary and secondary master
• mdamd, utility for configuring RAID

Contents 1 Preparation 2 Installation 2.1 Install grub on both disk 2.2 Partition 3 Configuration 4 Remove a partition from an array 5 Replacing a faulty disk 6 mdadm 7 References

[edit] Preparation

First, if you are installing for the first time, get yourself familiar with the technical information (see references below).

[edit] Installation

This information is based on a fresh install of CentOS 4.4 from the ServerCD.

[edit] Install grub on both disk

grub
 root (hd0,0)
 setup (hd0)
 root (hd1,0)
 setup (hd1)
 quit

[edit] Partition

• Choose Disk Druid when entering the Disk Partitioning Setup to setup the partition manually.
• Select hda1 and edit it

[edit] Configuration

[edit] Remove a partition from an array

Fail the partition

mdadm --fail /dev/md1 /dev/sda1

Remove the partition

mdadm -r /dev/md1 /dev/sda1

[edit] Replacing a faulty disk

Add an identical disk and start up system.

/dev/sda - existing disk

/dev/sdb - new disk

• Clone partition from sda to sdb

sfdisk -l
sfdisk -d /dev/sda | sfdisk /dev/sdb
sfdisk -l

Double check before executing, this can destroy data.

• Re-setup RAID

mdadm -a /dev/md0 /dev/sdb1

Add the right RAID partition to the respective RAID device use this to check

cat /proc/mdstat

[edit] mdadm

Some useful commands:

• mdadm --detail /dev/md0

Remove a faulty device

• mdadm -r /dev/md0 /dev/sda2

Add a device

• mdadm -a /dev/md0 /dev/sda2

[edit] References

System Administration Guide:

• Chapter 7 Logical Volume Manager (LVM)
• Chapter 8 LVM Configuration
• Chapter 9 Redundant Array of Independent Disks (RAID)
• Chapter 10. Software RAID Configuration