Setting up RAID 1 (Mirroring) using ‘Two Disks’ in Linux – Part 3

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Babin Lonston

I'm Working as a System Administrator for last 10 year's with 4 years experience with Linux Distributions, fall in love with text based operating systems.

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66 Responses

  1. Rajarao says:

    Thank you ! Excellent Tutorials! I was able to understand with no tech background, Do you have any AWS questions dump for Solution Architect Associate exam.

  2. Swaraj says:

    mdadm E showing raid super block already exists. What is the procedure to clean it and use device for another raid level?

  3. Amar G says:

    Thank you so much Bobin. I always follow when I have any doubt and I want to clear that. Really your lots of articles are very useful for me.

  4. Vishal Bajpai says:

    Why Raid is configured of partitioned disk, if we can do it on disk itself? Why extra efforts in creating partition?

  5. Clark kent says:

    It is possible to RAID1 my existing HDD? I have 1 HDD running now I want to add HDD as mirror.

    • Babin Lonston says:


      No, You required to backup your data’s to create a DM device. Then try to setup a Raid 1.

      Thanks & Regards,
      Babin Lonston

  6. charly says:

    I use this tutorial all the time. THANKS!

    Here are some instructions for Debian at least, to delete a created raid and start from scratch (I had to, after messing up my NAS Debian)

  7. Arun says:

    Hello Babin,

    It is possible to create RAID configuration on ISCSI blocks?

    • Hi Arun,

      It’s possible, But the concept of RAID is failover. When a disk failed in the array it will be available.

      In real time environments, iSCSI blocks are created on top of some disk array which already running with Hardware RAID.

      Storage –> Disk Array in a RAID –> Create a iSCSI block –> Presented to your server.

      Thanks & Regards,
      Bobin Lonston

  8. Volkan Paksoy says:


    Thanks for the article, it’s been helpful to me to set up a RAID1. For some reason it automatically renamed it to /dev/md127. After I modified the fstab file accordingly it worked fine.

    A problem happens though when I try to test it. I’m using a physical machine. I shutdown the machine and unplugged one of the drives but it didn’t reboot properly. I had to connect a monitor and keyboard as I think it booted into a emergency mode or something like that, SSH is not running at that stage.

    Anyway, when I run mdadm –detail /dev/md127 the state is inactive.
    So in a real world scenario how will I be able to replace a disk and add it to the RAID? Any ideas?

    Thanks again for the article.

    • Volkan Paksoy says:

      In my experience unplugging the drive didn’t work. But if I run this command before unplugging.

      # mdadm --manage /dev/md0 --remove /dev/sdb1

      then it boots just fine and the RAID becomes degraded. Then a new disk can be added.

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