Create RAID Arrays with mdadm on Ubuntu

Last step editing the fstab echo ‘/dev/md0 /mnt/md0 ext4 defaults,nofail,discard 0 0’ | sudo tee -a /etc/fstab

should be

echo ‘/dev/md0 /mnt/md0 ext4 defaults,nofail,discard 0 2’ | sudo tee -a /etc/fstab

The 2 in the 0 space allows the system to boot the main os first then the array after. If left to 0 there is reports (and experienced myself) of the array not assembling in enough time before the system fully boots resulting in the nofail trigger to never report why it did not load. This is shown here fstab(5) - Linux manual page (man7.org)

Hi, thank you for this awesome tutorial (and others).

On a new Ubuntu 22.04 install I created a RAID 10 array per your code (sudo mdadm --create --verbose /dev/md0 --level=10 --layout=f2 --raid-devices=4 /dev/sda /dev/sdb /dev/sdc /dev/sdd) using f2 for a far/2-copies setup on a 4Tb x 4 array to get approx. 8Tb. I’ve created/mounted/saved per all of your instructions. I also set USB shares to mount at /media/ instead of /media/user/ per this tutorial. I started yesterday afternoon and currently when I run “cat /proc/mdstat” the resync = 13.7%.

My 2 questions, please and thank you:

Do I need to keep this computer on until the resync is finished, or can I reboot and assume it will continue where it left off?

At what point can I add md0 to Samba and start copying data onto the new array?

Newbie here, sorry:(

OK so I have followed this how-to several times now but seem to have ongoing issues with the array stability? Today I went to access the array as I had copied 1.5TB of data to it and it wasn’t accessible? Said the super block was unreadable and I could not save the array. So now I am rebuilding it again as a Raid 6 volume. Currently waiting for the build to finish. I read the comment below about changing the 0 to a 2 so that the array would load at boot time and used that config. Is this causing me issues? I am running Ubuntu 22.04.3 LTS with a 256gb SSD OS drive and the 4 834gb SSD drives for the array which gives me a 1.7tb disk for storage. I am not a big Linux guy my day job is Windows admin so this stuff is a bit foreign to me. I am using this as a Photoprism photo respository and don’t want to get all my photos on the array only to lose them down the road? Any help is much appreciated.

After following this guide for RAID 0 my RAID was not coming up automatically after reboot. I created the RAID on the partition instead of the device (used sda1 instead of sda) and it’s working now.

There should be a section added to resetting devices. For drives that were formatted GTP there is a possibility that they will loose their superblock upon reboot causing the array to fail. This can be cleared off by sgdisk --zap /dev/sdX I spent a few days trying to figure out why my raid5 array wouldn’t survive reboot. This fixed the problem by clearing whatever corrupted partition data was on the drive.

First, congrats on and thanks for an excellent article. Just what I need, as I want to implement a software raid at home.

I hate to be pedantic…

You have a typesetting issue above. In the code boxes, up in the first section on resetting the drives for the array, when you show a pathntame, such as /dev/sda, or /dev/whatever, your html causes a gap to appear that looks like a space between /dev/ and whatever follows. This looks to a beginner like a space. If you use the copy button, or copy manually, the path is correct in the copy buffer, but if you are retyping, you may be tricked into thinking that there is an extra separate argument.

The HTML is more intricate right there.

<span class="token parameter variable">--stop</span> /dev/<mark>md0</mark>

It’s the <mark> that does it.

This is on Chrome using a Chromebook.

Hi team,

If I got this heading where if I copied it, it will link up to the wrong heading

Creating and Mounting the Filesystem

It will link to:

Creating a RAID 0 Array

It needs to link to the sub heading in here as I am using RAID1 only, thanks.

Creating a RAID 1 Array