16.7. Creating a software RAID on an installed system

Procedure

1. Create a RAID of two block devices, for example /dev/sda1 and /dev/sdc1:

   # mdadm --create /dev/md0 --level=0 --raid-devices=2 /dev/sda1 /dev/sdc1
   mdadm: Defaulting to version 1.2 metadata
   mdadm: array /dev/md0 started.

   The level_value option defines the RAID level.

2. Optional: Check the status of the RAID:

   # mdadm --detail /dev/md0
   /dev/md0:
              Version : 1.2
        Creation Time : Thu Oct 13 15:17:39 2022
           Raid Level : raid0
           Array Size : 18649600 (17.79 GiB 19.10 GB)
         Raid Devices : 2
        Total Devices : 2
          Persistence : Superblock is persistent
   
          Update Time : Thu Oct 13 15:17:39 2022
                State : clean
       Active Devices : 2
      Working Devices : 2
       Failed Devices : 0
        Spare Devices : 0
   [...]

3. Optional: Observe the detailed information about each device in the RAID:

   # mdadm --examine /dev/sda1 /dev/sdc1
   /dev/sda1:
             Magic : a92b4efc
           Version : 1.2
       Feature Map : 0x1000
        Array UUID : 77ddfb0a:41529b0e:f2c5cde1:1d72ce2c
              Name : 0
     Creation Time : Thu Oct 13 15:17:39 2022
        Raid Level : raid0
      Raid Devices : 2
   [...]

4. Create a file system on the RAID drive:

   # mkfs -t xfs /dev/md0

   Replace xfs with the file system that you chose to format the drive with.

5. Create a mount point for RAID drive and mount it:

   # mkdir /mnt/raid1
   # mount /dev/md0 /mnt/raid1

   Replace /mnt/raid1 with the mount point.

   If you want that RHEL mounts the md0 RAID device automatically when the system boots, add an entry for your device to the /etc/fstab file:

   /dev/md0   /mnt/raid1 xfs  defaults   0 0