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
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
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
Although the following steps are illustrated during a GUI
installation, the same can be done during a text-based
Configuration of software RAID must be done manually in
Disk Druid during the installation
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
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
In Disk Druid, choose RAID to enter the software RAID creation
Choose 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
Figure 10-2. RAID Partition Options
A software RAID partition must be constrained to one drive. For
, 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
Enter the size that you want the partition to be.
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.
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
Click OK to return to the main
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