Creating and Managing a Software RAID

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Creating and Managing a Software RAID

RAID is used to combine multiple devices into one or more logical units. In this hands-on lab, we are tasked with creating a RAID 5 array, failing active devices and observing the behavior, and adding new devices to the RAID to replace the ones that have failed.

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Lab Info

Level

Intermediate

Last updated

Sep 24, 2025

Duration

30m

Challenge

Create a RAID 5 Array Based on the Instructions
Use the mdadm command to create the RAID 5 array.
```
mdadm -C /dev/md0 -l raid5 -n 3 /dev/xvdf1 /dev/xvdg1 /dev/xvdj1 -x 3 /dev/xvdf2 /dev/xvdg2 /dev/xvdj2
```
Create the mdadm.conf file to ensure the RAID is available on boot.
```
mdadm -D -s -v > /etc/mdadm.conf
```
Challenge

Create an Ext4 Filesystem, Mount It, and Ensure It Persists Through a Reboot
Use the mkfs command to create an ext4 filesystem on /dev/md0.
```
mkfs -t ext4 /dev/md0
```
Create the /mnt/raid mount point.
```
mkdir /mnt/raid
```
Mount /dev/md0 on /mnt/raid.
```
mount -t ext4 /dev/md0 /mnt/raid
```
Use the blkid command to obtain the UUID of /dev/md0:
```
blkid /dev/md0
```
Use a text editor to open /etc/fstab and add the following entry at the bottom of the file (using the UUID observed in the previous step):
```
UUID=uuid_of_md0    /mnt/raid    ext4    defaults    0 0
```
Challenge

Fail the Active Devices in the Array One at a Time and Remove Them
Fail the active devices using the -f option (Note: Wait until a spare device has been added to the array before proceeding to the next to prevent RAID failure. The state can be checked by running mdadm -D /dev/md0).
```
mdadm -f /dev/md0 /dev/xvdf1
mdadm -f /dev/md0 /dev/xvdg1
mdadm -f /dev/md0 /dev/xvdj1
```
Remove failed devices from the array.
```
mdadm -r /dev/md0 /dev/xvdf1 /dev/xvdg1 /dev/xvdj1
```
Challenge

Add Three New Devices to the Array Based on the Instructions
Add new devices to /dev/md0.
```
mdadm -a /dev/md0 /dev/xvdf3 /dev/xvdg3 /dev/xvdj3
```
Update /etc/mdadm.conf with new configuration changes.
```
mdadm -D -s -v > /etc/mdadm.conf
```

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