How to create software RAID array

When creating a software RAID array, you need to pay attention to preparing the disk, installing tools, selecting levels, formatting mounts, and configuration saving. First, confirm the hard disk status and install the mdadm tool. Ubuntu/Debian uses sudo apt install mdadm, and CentOS/RHEL uses sudo yum install mdadm; secondly, select the RAID level according to the needs (such as RAID 0, 1, 5, 6), execute the corresponding command to create an array, such as /dev/sdb and /dev/sdc to create RAID 1: sudo mdadm --create --verbose /dev/md0 --level=1 --raid-devices=2 /dev/sdb /dev/sdc; then format the RAID device to an ext4 file system and mount it, such as sudo mkfs.ext4 /dev/md0 and sudo mount /dev/md0 /mnt/raid; finally write RAID information to /etc/fstab to achieve automatic mount on the computer, and monitor the status through cat /proc/mdstat or sudo mdadm --detail /dev/md0, remove the old disk and add a new disk to rebuild the array. The entire process requires careful verification of the disk and configuration to avoid operational errors.

Creating a software RAID array is actually not difficult, but there are several key points to pay attention to. Operating system-level software RAID (such as Linux's mdadm ) can provide basic redundancy and performance improvements, suitable for scenarios without hardware RAID controllers.

Preparation: Confirm the hard drive and install the mdadm tool

Before you start, make sure you are ready for the disks you want to use and that they are unpartitioned or brand new. You can use the command lsblk or fdisk -l to view the disk status in the current system.

Also, most modern Linux distributions do not have mdadm installed by default, you need to install it manually:

• Ubuntu/Debian: sudo apt install mdadm
• CentOS/RHEL: sudo yum install mdadm

After the installation is complete, you can start creating the RAID array.

Create a RAID array: Select a level and execute the command

Choose the right RAID level according to your needs, the common ones are:

• RAID 0 : Stripe, improve performance, no redundancy
• RAID 1 : Mirroring, double-copy data storage, high security
• RAID 5/6 : Need at least 3 or 4 disks, with a certain amount of redundancy and performance balance

Taking creating RAID 1 as an example, suppose you want to use the two disks: /dev/sdb and /dev/sdc :

 sudo mdadm --create --verbose /dev/md0 --level=1 --raid-devices=2 /dev/sdb /dev/sdc

This command creates a RAID device named /dev/md0 . Note that some systems may need to partition the disk first and set the partition type to Linux RAID (code fd).

Format and Mount RAID Devices

After creation, the RAID device is just a bare device and needs to be formatted to use. For example, formatted as ext4 file system:

 sudo mkfs.ext4 /dev/md0

Then you can choose to mount it to a directory, such as /mnt/raid :

 sudo mount /dev/md0 /mnt/raid

If you want to automatically mount on the computer, remember to write the relevant information to /etc/fstab , and also save the RAID configuration to /etc/mdadm.conf or use the tools provided by the distribution.

Manage and monitor RAID status

During daily maintenance, you can view the RAID status in the following ways:

 cat /proc/mdstat

Or use the mdadm command to view the details:

 sudo mdadm --detail /dev/md0

If a disk fails, it can be removed from the array and replaced:

 sudo mdadm --remove /dev/md0 /dev/sdb
sudo mdadm --add /dev/md0 /dev/sdb_new

The RAID reconstruction process will start automatically, but performance may decline during the period, and it is recommended to operate during the low peak period.

Basically all this is it. The whole process is not complicated, but the details are prone to errors, especially the step of disk selection and configuration saving. You must check carefully.

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