How to convert linear root disk to RAID1 on RHEL 7 and higher on Power Systems post-install?

Solution Verified - Updated 2 Dec 2025

Environment

Red Hat Enterprise Linux 7,8,9,10
Power Systems (ppc64/ppc64le)

Issue

How do I convert my root disk to RAID1 post installation of Red Hat Enterprise Linux 7/8/9/10 on power systems?

Resolution

This guide assumes you are utilizing the default partition scheme, but the steps can be modified to match any type of configuration.
This guide assumes that /dev/vda is your main disk, and that it needs to be in a mirror with /dev/vdb.
Downtime will be required for this operation. This will cause problems if attempted in a live production environment. It would be recommend to please backup the critical data and verify the backup before making any changes to the underlying storage, lvm or filesystem to avoid any unforeseen problem.
Note: This procedure, along with any that involves moving /boot or /across devices (except via pvmove), is unsupported. Please ensure you take proper backups before attempting this procedure.

Gather the partition information from your main disk /dev/vda:

# parted /dev/vda u s p 
Model: Virtio Block Device (virtblk)
Disk /dev/vda: 31457280s
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags: 

Number  Start     End        Size       Type     File system  Flags
 1      2048s     10239s     8192s      primary               boot, prep
 2      10240s    2107391s   2097152s   primary  xfs
 3      2107392s  31457279s  29349888s  primary               lvm

Using the start and end sectors, reproduce the partitioning scheme from the previous command on the new unused disk:

# parted /dev/vdb mklabel msdos
# parted /dev/vdb mkpart primary 2048s 10239s
# parted /dev/vdb mkpart primary 10240s 2107391s
# parted /dev/vdb mkpart primary 2107392s 31457279s

Copy the contents of the PowerPC Reference Platform (PReP) boot partition from /dev/vda1 to /dev/vdb1:
```
# dd if=/dev/vda1 of=/dev/vdb1
```

Update the prep and boot flag on the first partition of both disks and add lvm flag on third partition of new disk:

    # parted /dev/vda set 1 prep on
    # parted /dev/vda set 1 boot on
    # parted /dev/vdb set 1 prep on
    # parted /dev/vdb set 1 boot on

    # parted /dev/vda set 2 raid on
    # parted /dev/vdb set 2 raid on
    # parted /dev/vda set 3 raid on
    # parted /dev/vdb set 3 raid on

Create a degraded RAID device on the second partition of the new disk (Note: 1st partition will be PReP so we cannot bring it under raid). 2nd Partition will be used for boot partition (/boot).
```
# mdadm --create /dev/md0 --level=1 --raid-disks=2 missing /dev/vdb2 
```
Create file-system same as existing on /dev/vda2 on the new degraded RAID array /dev/md0:
```
# mkfs.xfs /dev/md0 
```

Mount the new raid array and copy over the files from /boot:

# mkdir /mnt/md0
# mount /dev/md0 /mnt/md0
# rsync -a /boot/ /mnt/md0/
# sync
# umount /mnt/md0
# rmdir /mnt/md0

Unmount the current /boot, and mount the new RAID volume there:
```
# umount /boot
# mount /dev/md0 /boot
```
Add the old disk to the new array to complete the mirror:
```
# mdadm /dev/md0 -a /dev/vda2
```

Monitor the RAID status and wait for the recovery to complete:

# mdadm -D /dev/md0 
/dev/md0:
           Version : 1.2
     Creation Time : Thu Sep 25 21:13:18 2025
        Raid Level : raid1
        Array Size : 1048512 (1023.94 MiB 1073.68 MB)
     Used Dev Size : 1048512 (1023.94 MiB 1073.68 MB)
      Raid Devices : 2
     Total Devices : 2
       Persistence : Superblock is persistent

       Update Time : Thu Sep 25 21:17:09 2025
             State : clean 
    Active Devices : 2
   Working Devices : 2
    Failed Devices : 0
     Spare Devices : 0

Consistency Policy : resync

              Name : node3:0  (local to host node3)
              UUID : 2ea5e20b:4372f3f1:46a75165:9cafe86a
            Events : 35

    Number   Major   Minor   RaidDevice State
       2     252        2        0      active sync   /dev/vda2
       1     252       18        1      active sync   /dev/vdb2

Find UUID of /dev/md0 using blkid:

# blkid  |grep md0
/dev/md0: UUID="4eda1a61-6f5c-4a65-bf1a-c582cc7b27b5" BLOCK_SIZE="512" TYPE="xfs"

Update the /etc/fstab file with the new location for boot:

# grep boot /etc/fstab
#UUID=d0ba5a87-bae6-4c5c-a4f3-c13b9dcf312f /boot                   xfs     defaults        0 0
UUID=4eda1a61-6f5c-4a65-bf1a-c582cc7b27b5 /boot                   xfs     defaults        0 0

Create a degraded RAID device on the third partition of the new disk. This will be used for your LVM partition:
```
#  mdadm --create /dev/md1 --level=1 --raid-disks=2 missing /dev/vdb3 --metadata=1.2
```
Add this new array to your LVM stack and add it to your existing volume group:
```
# vgextend rhel /dev/md1 
  Physical volume "/dev/md1" successfully created
  Volume group "rhel" successfully extended
```
Note: mdadm metadata version 1.2 places the RAID superblock at 4K from the beginning of the disk and creates a reserved metadata area. This area size can vary depending on the actual array size AND can actually affect the PV allocation that is created on the disk. If you encounter an issue where pvmove returns insufficient extent in the next few steps, perform the following to workaround the issue. Alternatively, remove the swap volume and recreate it with a few megabytes less space so that it correctly fits within the physical volume.

14.a Remove the md device from the VG and stop it:
```
# vgreduce rhel /dev/md1
# mdadm --stop /dev/md1
```
14.b Recreate the md device with metadata set to version 1.0, ignore any warning messages:
```
# mdadm --create /dev/md1 --level=1 --raid-disks=2 missing /dev/vdb3 --metadata=1.0
```
14.c Add the device back to the VG:
```
# vgextend rhel /dev/md1
```
Move the physical extents from the old partition to the new array:
```
#  pvmove --atomic /dev/vda3 /dev/md1
```
Remove the old partition from the volume group and LVM stack:
```
# vgreduce rhel /dev/vda3 
# pvremove /dev/vda3
```
[Only for RHEL7] There are some known issue with lvmetad cache so it's better to disable lvmetad cache.
Modify use_lvmetad as below in lvm.conf:
```
	use_lvmetad = 1
        to
	use_lvmetad = 0
```
Stop lvm2-lvmetad service:
```
$ systemctl stop lvm2-lvmetad.service
$ systemctl disable lvm2-lvmetad.service
```
Add the old partition to the degraded array to complete the mirror:
```
# mdadm /dev/md1 -a /dev/vda3
```

Monitor the RAID status and wait for the recovery to complete:

# mdadm -D /dev/md1 
/dev/md1:
           Version : 1.2
     Creation Time : Thu Sep 25 21:21:45 2025
        Raid Level : raid1
        Array Size : 14674816 (13.99 GiB 15.03 GB)
     Used Dev Size : 14674816 (13.99 GiB 15.03 GB)
      Raid Devices : 2
     Total Devices : 2
       Persistence : Superblock is persistent

       Update Time : Thu Sep 25 21:47:49 2025
             State : clean 
    Active Devices : 2
   Working Devices : 2
    Failed Devices : 0
     Spare Devices : 0

Consistency Policy : resync

              Name : node3:1  (local to host node3)
              UUID : dbabe015:0d22b1a3:0dc8f2a8:b2323b60
            Events : 89

    Number   Major   Minor   RaidDevice State
       2     252        3        0      active sync   /dev/vda3
       1     252       19        1      active sync   /dev/vdb3

[Only for RHEL9 and RHEL10] Update the raid device in lvm system.devices file.
```
 # lvmdevices  --deldev /dev/vda3 
 # lvmdevices  --adddev /dev/md1 
```
Scan mdadm metadata and append RAID information to /etc/mdadm.conf:
```
# mdadm --examine --scan > /etc/mdadm.conf
```

Update /etc/default/grub with MD device UUID:

# mdadm -D /dev/md* |grep UUID
              UUID : 2ea5e20b:4372f3f1:46a75165:9cafe86a
              UUID : dbabe015:0d22b1a3:0dc8f2a8:b2323b60

# grep GRUB_CMDLINE_LINUX /etc/default/grub 
#GRUB_CMDLINE_LINUX="rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap rhgb quiet"
GRUB_CMDLINE_LINUX="rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap rhgb quiet rd.md.uuid=2ea5e20b:4372f3f1:46a75165:9cafe86a rd.md.uuid=dbabe015:0d22b1a3:0dc8f2a8:b2323b60"

Update grub2.cfg:

 # grub2-mkconfig -o /boot/grub2/grub.cfg

Use below command to update grub configuration in RHEL9 and RHEL10.

```
# grub2-mkconfig -o /boot/grub2/grub.cfg --update-bls-cmdline
```

Verify that both of your disks are listed in /boot/grub/device.map. Add them if needed.
```
  # cat /boot/grub2/device.map
   (hd0)      /dev/vda
   (hd1)      /dev/vdb
```
Reinstall grub2-ppc64le and grub2-ppc64le-modules package and then run grub2-install (Ignore the warning it reports while running grub2-install command for prep partition):
```
# yum reinstall grub2-ppc64le grub2-ppc64le-modules -y
# grub2-install /dev/vda1
# grub2-install /dev/vdb1
```
Note: Here we used ppc64le package as test system was ppc64le architecture but if its ppc64 then use grub2-ppc64 and grub2-ppc64-modules package.
Rebuild initramfs image with mdadmconf.
It is recommended to make a backup of initramfs in case the new version has an unexpected problem:
```
$ cp /boot/initramfs-$(uname -r).img /boot/initramfs-$(uname -r).img.$(date +%m-%d-%H%M%S).bak
# dracut -f --mdadmconf
```
Reboot the machine to make sure everything is correctly utilizing the new software RAID devices.

SBR

Product(s)

Red Hat Enterprise Linux

Components

Category

Configure

Tags

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