Create And Manage RAID Array On Ubuntu 20.04

02 November 2021 - 5 mins read time
Tags: Ubuntu Linux

RAID Array

RAID devices are virtual devices created from two or more real block devices. This allows multiple devices (typically disk drives or partitions thereof) to be combined into a single device to hold (for example) a single filesystem. Some RAID levels include redundancy and so can survive some degree of device failure.. It will support user to improve performance and backup when using disks as virtual storage.

Linux supports LINEAR md devices, RAID0 (striping), RAID1 (mirroring), RAID4, RAID5, RAID6, RAID10, MULTIPATH, FAULTY, and CONTAINER. In this post, I will help you create and manage RAID array with 0, 1 and 5 on Ubuntu 20.04 (others are same)

Check RAID status and show the device infomation

Check RAID status

You can easily check with the following command:

cat /proc/mdstat

Output

Show devices which were used to build or not build the RAID array

Type the following command:

lsblk -o NAME,SIZE,FSTYPE,TYPE,MOUNTPOINT

Install mdadm

mdadm - manage MD devices aka Linux Software RAID. More info about RAID and mdadm

mdadm [mode] <raiddevice> [options] <component-devices>

Get the infomation of RAID on device

To get the infomation of RAID on your device, you can:

`sudo mdadm -E /dev/md0

Create RAID array

You can create a RAID array and custom some demand such as RAID level, amount of devices,…

I will use sdb and sdc device to create RAID 0:

sudo mdadm --create --verbose /dev/md0 --level=0 --raid-devices=2 /dev/sdb /dev/sdc

Output

After create the RAID array, you need to create the filesystem and mount it into the folder

Create file system

Type the command:

sudo mkfs.ext4 -F /dev/md0

Output

Create a mount point and mount into the folder

Use mkdir to create a mountpoint:

sudo mkdir -p /mnt/md0

And mount /dev/md0 into /mnt/md0:

sudo mount /dev/md0 /mnt/md0

Save and config a automatic reassemble and mount RAID array

I was create a RAID array, and I wanna that the RAID array will be automatic reassembled at boot:

sudo mdadm --detail --scan | sudo tee -a /etc/mdadm/mdadm.conf

Output

Next, I need that it will be automatic mounted:

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

Output

Finally, we need to update init ram file system:

sudo update-initramfs -u

If you do right, you will see the output which is used when you type lsblk command:

Output

If you want to know how I create the RAID 1, 5, you can watch the video which I attached it on the top of page ^^

Manage RAID array/auto-mount

Now, I will manage RAID array with add, remove and reset a RAID array

Reset a RAID array

Before you reset a RAID, you had to umount it:

sudo umount /dev/md0

Next, let’s use mdadm to stop and remove it:

sudo mdadm --stop /dev/md0
sudo mdadm --remove /dev/md0

Output

Now, the /dev/md0 is stopped and removed from RAID array. We try to check it:

Output

As you can see that, it’s not yet clear. So we can use --zero-superblock to full reset:

sudo mdadm --zero-superblock /dev/sdb
sudo mdadm --zero-superblock /dev/sdc

Done:

Output

Next, you need to edit the mdadm config file and fstable file because you were config it to automatic reassemble and mount before:

sudo nano /etc/fstab

The nano will appear and you need to comment or earase the ARRAY info:

Output

sudo nano /etc/mdadm/mdadm.conf

Comment or earase the FSTAB info:

Output

And let’s update the init ram fs now to finish ^^

sudo update-initramfs -u

Add a devide into RAID array

I will add a device on RAID 5. Note that the RAID 5 have at least 3 devices. I will add the sde device to the RAID 5:

sudo mdadm /dev/md0 --add /dev/sde

After that, we need to comment with # in mdadd.conf file as same as resetting step:

sudo nano /etc/mdadm/mdadm.conf

Append new RAID info into the file to mdadm reassemble array:

sudo mdadm --detail --brief /dev/md0 | sudo tee -a /etc/mdadm/mdadm.conf

Now the RAID have 4 active devices but only have 3 working devices. You need to grow up the RAID with:

sudo mdadm --grow /dev/md0 --raid-devices=4 --add /dev/sde

And resize the filesystem:

sudo resize2fs /dev/md0

Output

Remove a devide from RAID array

Before you remove a devices from RAID array, you must to fail it first with:

sudo mdadm /dev/md0 --fail /dev/sde

Next, let’s remove it:

sudo mdadm /dev/md0 --remove /dev/sdc

After you remove the device, you need to re-edit the fstab file and mdadm file as same as previous part. Now, you were remove the devices succesfully ^^

Good luck <3

Note and reference