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

Chapter 10. Software RAID Configuration

Software RAID can be configured during the graphical installation process, the text-based installation process, or during a kickstart installation. This chapter discusses how to configure software RAID during installation, using the Disk Druid interface.

Read Chapter 9 Redundant Array of Independent Disks (RAID) first to learn about RAID, the differences between hardware and software RAID, and the differences between RAID 0, 1, and 5. An overview of the steps required to configure RAID include:

  • Applying software RAID partitions to the physical hard drives.

    If you wish to have the boot partition (/boot/) reside on a RAID parition, it must be on a RAID 1 partition.

  • Creating RAID devices from the software RAID partitions.

  • Optional: Configuring LVM from the RAID devices. Refer to Chapter 8 LVM Configuration for more information on configuring LVM after first configuring RAID.

  • Creating file systems from the RAID devices.

Note Note
 

Although the following steps are illustrated during a GUI installation, the same can be done during a text-based installation.

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

Two 9.1 GB SCSI drives (/dev/sda and /dev/sdb) are used in the following examples. 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.

10.1. 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 10-1.

Figure 10-1. 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 10-2. Note that no other RAID options (such as entering a mount point) are available until RAID partitions, as well as RAID devices, are created.

    Figure 10-2. RAID Partition Options

  3. A software RAID partition must be constrained to one drive. For Allowable Drives, select the drive on which RAID is to be created. If you have multiple drives, all drives are selected, and you must deselect all but one drive.

    Figure 10-3. Adding a RAID Partition

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

  5. Select Fixed size to make the partition the specified size, select Fill all space up to (MB) and enter a size in MBs to give range for the partition size, or select Fill to maximum allowable size to make it grow to fill all available space on the hard disk. If you make more than one partition 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. Click OK to return to the main screen.

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 10-4 shows successfully allocated space for the RAID 1 configuration (for /boot/), which is now ready for RAID device and mount point creation:

Figure 10-4. RAID 1 Partitions Ready, Pre-Device and Mount Point Creation

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