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.
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
Optional: Configuring LVM
from the RAID devices.
Creating file systems from the RAID
Although this procedure covers installating with a GUI
application, system administrators can do the same with
Configuration of software RAID must be done manually in
Disk Druid during the
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.
Figure 4.1. Two Blank Drives, Ready For Configuration
In Disk Druid,
choose RAID to enter
the software RAID creation screen.
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,
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.
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.
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
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:
Figure 4.6. Making a RAID Device and Assigning a Mount Point
Select a mount point.
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
(LVM). If LVM is not required, continue on with
the following instructions.
Select a device name such as md0 for the RAID device.
Choose your RAID level. You can choose from RAID 0,
RAID 1, and RAID
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
The RAID partitions created appear in the RAID Members list. Select which
of these partitions should be used to create the RAID
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).
After clicking OK,
the RAID device appears in the Drive Summary list.
Repeat this chapter's entire process for configuring
additional partitions, devices, and mount points, such as
the root partition (/),
/home/, or swap.