Linux Setting up a software RAID1 system for a complete mirror

To set up a software RAID1 (mirror) system in Linux, you will need to use the mdadm command.

Before setting up the RAID array, you will need to prepare the disks that will be used in the array. This involves partitioning the disks and creating a file system on each partition.

Here are the steps to set up a software RAID1 system for a complete mirror:

1. Partition the disks using a partitioning tool such as fdisk or parted. Make sure to create partitions of the same size on both disks.

2. Create a file system on each partition. For example, to create an ext4 file system on the first partition of the first disk, you can use the following command:

mkfs.ext4 /dev/sda1

Repeat this step for the other partition.

3. Create the RAID1 array using the mdadm command. For example, to create a RAID1 array named /dev/md0 using the partitions /dev/sda1 and /dev/sdb1, you can use the following command:

sudo mdadm --create /dev/md0 --level=mirror --raid-devices=2 /dev/sda1 /dev/sdb1

4. Wait for the RAID array to be initialized. This may take a few minutes depending on the size of the disks.

5. Create a file system on the RAID array. For example, to create an ext4 file system on the RAID array, you can use the following command:

sudo mkfs.ext4 /dev/md0

6. Create a mount point for the RAID array, and mount the array to the mount point. For example, to create a mount point at /mnt/raid and mount the array to it, you can use the following commands:

sudo mkdir /mnt/raid
sudo mount /dev/md0 /mnt/raid

7. Add an entry to the /etc/fstab file to mount the RAID array automatically at boot time. Open the file in a text editor:

sudo nano /etc/fstab

Add the following line to the end of the file:

/dev/md0 /mnt/raid ext4 defaults 0 0

After completing these steps, the RAID1 array will be set up and ready to use. You can access the array by navigating to the mount point (e.g., /mnt/raid). Any data written to the array will be automatically mirrored to both disks.

Keep in mind that software RAID is implemented in software, and can be slower than hardware RAID. It is also more vulnerable to data loss if one of the disks fails. To ensure data integrity, you should regularly check the status of the RAID array using the mdadm command, and replace failed disks as needed.