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NOTE: CentOS Enterprise Linux 5 is built from the Red Hat Enterprise Linux source code. Other than logo and name changes CentOS Enterprise Linux 5 is compatible with the equivalent Red Hat version. This document applies equally to both Red Hat and CentOS Enterprise Linux 5.

4.5. Configuring Software RAID

Users can configure Software RAID during the graphical installation process (Disk Druid), the text-based installation process, or during a kickstart installation.This chapter covers Software RAID configuration during the installation process using the Disk Druid application.

  • Apply software RAID partitions to the physical hard drives.

    To add a boot partition (/boot/) to a RAID partition, ensure it is on a RAID1 partiton.

  • Creating RAID devices from the software RAID partitions.

  • Optional: Configuring LVM from the RAID devices.

  • Creating file systems from the RAID devices.


Although this procedure covers installating with a GUI application, system administrators can do the same with text-based installation.

Configuration of software RAID must be done manually in Disk Druid during the installation process.

These examples use two 9.1 GB SCSI drives (/dev/sda and /dev/sdb) to illustrate the creation of simple RAID1 configurations. They detail how to create a simple RAID 1 configuration by implementing multiple RAID devices.

On the Disk Partitioning Setup screen, select Manually partition with Disk Druid.

4.5.1. Creating the RAID Partitions

In a typical situation, the disk drives are new or are formatted. Both drives are shown as raw devices with no partition configuration in Figure 4.1, “Two Blank Drives, Ready For Configuration”.

Two Blank Drives, Ready For Configuration

Figure 4.1. Two Blank Drives, Ready For Configuration

  1. In Disk Druid, choose RAID to enter the software RAID creation screen.

  2. Choose Create a software RAID partition to create a RAID partition as shown in Figure 4.2, “RAID Partition Options”. Note that no other RAID options (such as entering a mount point) are available until RAID partitions, as well as RAID devices, are created.

    RAID Partition Options

    Figure 4.2. RAID Partition Options

  3. A software RAID partition must be constrained to one drive. For Allowable Drives, select the drive to use for RAID. If you have multiple drives, by default all drives are selected and you must deselect the drives you do not want.

    Adding a RAID Partition

    Figure 4.3. Adding a RAID Partition

  4. Enter the size that you want the partition to be.

  5. Select Fixed Size to specify partition size. Select Fill all space up to (MB) and enter a value (in MB) to specify partition size range. Select Fill to maximum allowable size to allow maximum available space of the hard disk. Note that if you make more than one space growable, they share the available free space on the disk.

  6. Select Force to be a primary partition if you want the partition to be a primary partition. A primary partition is one of the first four partitions on the hard drive. If unselected, the partition is created as a logical partition. If other operating systems are already on the system, unselecting this option should be considered. For more information on primary versus logical/extended partitions, refer to the appendix section of the Red Hat Enterprise Linux Installation Guide.

  7. Repeat these steps to create as many partitions as you need for your partitions.

Repeat these steps to create as many partitions as needed for your RAID setup. Notice that all the partitions do not have to be RAID partitions. For example, you can configure only the /boot/ partition as a software RAID device, leaving the root partition (/), /home/, and swap as regular file systems. Figure 4.4, “RAID 1 Partitions Ready, Pre-Device and Mount Point Creation” shows successfully allocated space for the RAID 1 configuration (for /boot/), which is now ready for RAID device and mount point creation:

RAID 1 Partitions Ready, Pre-Device and Mount Point Creation

Figure 4.4. RAID 1 Partitions Ready, Pre-Device and Mount Point Creation

4.5.2. Creating the RAID Devices and Mount Points

Once you create all of your partitions as Software RAID partitions, you must create the RAID device and mount point.

  1. Select the RAID button on the Disk Druid main partitioning screen (refer to Figure 4.5, “RAID Options”).

  2. Figure 4.5, “RAID Options” appears. Select Create a RAID device.

    RAID Options

    Figure 4.5. RAID Options

  3. Next, Figure 4.6, “Making a RAID Device and Assigning a Mount Point” appears, where you can make a RAID device and assign a mount point.

    Making a RAID Device and Assigning a Mount Point

    Figure 4.6. Making a RAID Device and Assigning a Mount Point

  4. Select a mount point.

  5. Choose the file system type for the partition. At this point you can either configure a dynamic LVM file system or a traditional static ext2/ext3 file system. For more information on configuring LVM on a RAID device, select physical volume (LVM). If LVM is not required, continue on with the following instructions.

  6. Select a device name such as md0 for the RAID device.

  7. Choose your RAID level. You can choose from RAID 0, RAID 1, and RAID 5.


    If you are making a RAID partition of /boot/, you must choose RAID level 1, and it must use one of the first two drives (IDE first, SCSI second). If you are not creating a seperate RAID partition of /boot/, and you are making a RAID partition for the root file system (/), it must be RAID level 1 and must use one of the first two drives (IDE first, SCSI second).

    The /boot/ Mount Error

    Figure 4.7. The /boot/ Mount Error

  8. The RAID partitions created appear in the RAID Members list. Select which of these partitions should be used to create the RAID device.

  9. If configuring RAID 1 or RAID 5, specify the number of spare partitions. If a software RAID partition fails, the spare is automatically used as a replacement. For each spare you want to specify, you must create an additional software RAID partition (in addition to the partitions for the RAID device). Select the partitions for the RAID device and the partition(s) for the spare(s).

  10. After clicking OK, the RAID device appears in the Drive Summary list.

  11. Repeat this chapter's entire process for configuring additional partitions, devices, and mount points, such as the root partition (/), /home/, or swap.

After completing the entire configuration, the figure as shown in Figure 4.8, “Final Sample RAID Configuration” resembles the default configuration, except for the use of RAID.

Final Sample RAID Configuration

Figure 4.8. Final Sample RAID Configuration

The figure as shown in Figure 4.9, “Final Sample RAID With LVM Configuration” is an example of a RAID and LVM configuration.

Final Sample RAID With LVM Configuration

Figure 4.9. Final Sample RAID With LVM Configuration

You can continue with your installation process. Refer to the Red Hat Enterprise Linux Installation Guide for further instructions.

  Published under the terms of the GNU General Public License Design by Interspire