The Linux kernel has native soft RAID capabilities, though I recommend using a hardware RAID controller when possible. When raid devices are created, they appear to the system as /dev/mdX where X=0-12. Once they are created, they act like any other device to the system and the RAID happens in the background.

The first step to creating a RAID device is to define it in the RAID configuration file, /etc/raidtab. Here is a sample configuration for RAID1 (mirroring) using two IDE disks:

        raiddev /dev/md0
            raid-level 1
            nr-raid-disks 2
            persistent-superblock 0
            chunk-size 8

            device /dev/hda1
            raid-disk 0
            device /dev/hdb1
            raid-disk 1

Here is a sample configuration for RAID5 (striping with parity) using three SCSI disks:

        raiddev /dev/md1
            raid-level 5
            nr-raid-disks 3
            nr-spare-disks 1
            persistent-superblock 1
            parity-algorithm left-symmetric

            device /dev/sda1
            raid-disk 0
            device /dev/sdb1
            raid-disk 1
            device /dev/sdc1
            raid-disk 2
            device /dev/sdd1
            spare-disk 0

Once the raidtab is defined, use mkraid to initialize and create the RAID sets. Caution: it is destructive to any data on the devices used.

To start all RAID devices in /etc/raidtab:

raidstart -a

To stop a RAID device:

raidstop /dev/mdX

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Most distributions start all defined RAID devices at boot time. In Red Hat Enterprise Linux, RAID devices are started from the /etc/rc.d/rc.sysinit boot script.