# How to Create Different RAID Array Levels on Linux In this tutorial, we'll guide you through how to create a new redundant array of independent disks (RAID) array, while leaving your existing RAID array untouched. Creating two separate RAID arrays improves your system's redundancy and performance for different data sets. This guide focuses on RAID 1, but the core principles can be applied to configure any RAID setup that suits your needs. Root (sudo) access is essential to perform these operations outlined in this guide. ## What Are the RAID Levels and Their Disk Requirements? RAID arrays come in different configurations designed to improve performance, redundancy, or both. Here are some key points to consider: #### RAID 0 - Minimum number of drives: 2 - Disk failure tolerance: No tolerance. If any drive fails, all data is lost. #### RAID 1 - Minimum number of drives: 2 - Disk failure tolerance: One drive failure can be tolerated without data loss, as the data is mirrored on the other drive. #### RAID 5 - Minimum number of drives: 3 - Disk failure tolerance: One drive failure can be tolerated. Data can be reconstructed from the information stored on the remaining drives. #### RAID 10 - Minimum number of drives: 4 - Disk Failure Tolerance: Each mirrored pair can tolerate up to one drive failure. Multiple drive failures can be tolerated if they are in different mirrored pairs. ## Instructions to Create New RAID Arrays ### Step 1: Prepare Your Drives Identify the drives connected to your system and determine which are available for the creation of a RAID array. This involves ensuring the drives are unmounted and not part of any existing RAID configuration. Unmounting drives will not cause data loss by itself, however, creating a RAID array using a drive will result in the loss of any data stored there. Ensure you have backups if necessary. 1. List all block devices. Use the “*lsblk*” command to list all block devices, their mount points, and their current usage. Look for devices that are not mounted or part of another RAID array. ```bash command lsblk ``` 2. Unmount the drives. Make sure the drives you want to use are not mounted. If they are, unmount them using the “umount” command, replacing “*/dev/sdX*” with the chosen drive name: ```bash command sudo umount /dev/sdX ``` 3. Check for existing RAID configurations. Use the following command to see the status of any existing RAID arrays. If the drives you want to use are part of an existing array, you must remove them before proceeding: ```bash command cat /proc/mdstat ``` An example output would be: ```bash output root@fphtaeqnyi-nxwtgsavpf:~# cat /proc/mdstat Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10] md0 : active raid1 nvme0n1p2[0] nvme1n1p1[1] 937049088 blocks super 1.2 [2/2] [UU] [====>................] resync = 35.9% (336969216/937049088) finish=48.4min speed=206513K/sec bitmap: 5/7 pages [20KB], 65536KB chunk unused devices: ``` 4. OPTIONAL - Clear previous RAID configurations: If a drive was previously part of a RAID array, you'll need to remove any remaining RAID metadata. Please note that this action will erase RAID metadata and any existing file systems on the drives, potentially resulting in data loss. You may skip this step if you are using fresh drives, or they have never been part of a RAID array. Use the following code to remove remaining RAID metadata, and replace "*/dev/sdX*" with the appropriate drive name. ```bash command sudo mdadm --zero-superblock /dev/sdX ``` Repeat this step for each drive you wish to use in the new RAID array. ### Step 2: Create the RAID Array Once the drives have been prepared, the next step is to create the RAID array. The following commands are provided for the creation of different RAID array types. #### For RAID 0 Replace "*mdX*" with your desired RAID device name and replace "*/dev/sdc*" and "*/dev/sd*" with the appropriate drive names. ```bash command sudo mdadm --create --verbose /dev/mdX --level=1 --raid-devices=2 /dev/sdc /dev/sdd ``` #### For RAID 1 Replace "mdX" with your desired RAID device name and replace "/dev/sdc" and "/dev/sdd" with the appropriate drive names. ```bash command sudo mdadm --create --verbose /dev/mdX --level=1 --raid-devices=2 /dev/sdc /dev/sdd ``` #### For Raid 5 Replace "mdX" with your desired RAID device name and replace "/dev/sdc," "/dev/sdd", and "/dev/sde" with the appropriate drive names. ```bash command sudo mdadm --create --verbose /dev/mdX --level=5 --raid-devices=3 /dev/sdc /dev/sdd /dev/sde ``` #### For Raid 10 Replace "mdX" with your desired RAID device name and replace "/dev/sdc", "/dev/sdd", "/dev/sde" and "/dev/sdf" with the appropriate drive names. ```bash command sudo mdadm --create --verbose /dev/mdX --level=10 --raid-devices=4 /dev/sdc /dev/sdd /dev/sde /dev/sdf ``` The process will appear similar to this RAID 1 array example: ```bash output root@fphtaeqnyi-nxwtgsavpf:~# sudo mdadm --create --verbose /dev/md1 --level=1 --raid-devices=2 /dev/nvme2n1 /dev/nvme3n1 mdadm: Note: this array has metadata at the start and may not be suitable as a boot device. If you plan to store '/boot' on this device please ensure that your boot-loader understands md/v1.x metadata, or use --metadata=0.90 mdadm: size set to 3750606144K mdadm: automatically enabling write-intent bitmap on large array Continue creating array? y mdadm: Defaulting to version 1.2 metadata mdadm: array /dev/md1 started. ``` ### Step 3: Check the RAID Array Status You can verify the status of the RAID array with the following command, replacing “*/dev/mdX*” with your RAID array device name: ```bash command sudo mdadm --detail /dev/mdX ``` This should return: ```Bash output root@fphtaeqnyi-nxwtgsavpf:~# sudo mdadm --detail /dev/md1 /dev/md1: Version : 1.2 Creation Time : Tue Jun 18 22:40:49 2024 Raid Level : raid1 Array Size : 3750606144 (3.49 TiB 3.84 TB) Used Dev Size : 3750606144 (3.49 TiB 3.84 TB) Raid Devices : 2 Total Devices : 2 Persistence : Superblock is persistent Intent Bitmap : Internal Update Time : Tue Jun 18 22:47:32 2024 State : clean, resyncing Active Devices : 2 Working Devices : 2 Failed Devices : 0 Spare Devices : 0 Consistency Policy : bitmap Resync Status : 2% complete Name : fphtaeqnyi-nxwtgsavpf:1 (local to host fphtaeqnyi-nxwtgsavpf) UUID : cf674ea9:d9a5c4d9:a7e67de1:f380cf54 Events : 79 Number Major Minor RaidDevice State 0 259 5 0 active sync /dev/nvme2n1 1 259 6 1 active sync /dev/nvme3n1 ``` ### Step 4: Save the RAID Configuration 1. Create a variable to store the UUID of the new RAID array. This command extracts the UUID of the new RAID array and stores it in a variable named “*NEW_UUID*”, simply replace “*/dev/mdX*” with your RAID array device name: ```bash command NEW_UUID=$(sudo mdadm --detail /dev/mdX | grep 'UUID' | awk '{print $3}') ``` 2. Append the new RAID array details to “*mdadm.conf*”. This command appends the new RAID array's details to the “mdadm.conf” file using the UUID stored in “$NEW_UUID” variable: ```bash command sudo mdadm --detail --scan | grep $NEW_UUID | sudo tee -a /etc/mdadm/mdadm.conf ``` You should see a similar output to: ```bash output root@fphtaeqnyi-nxwtgsavpf:~# NEW_UUID=$(sudo mdadm --detail /dev/md1 | grep 'UUID' | awk '{print $3}') root@fphtaeqnyi-nxwtgsavpf:~# sudo mdadm --detail --scan | grep $NEW_UUID | sudo tee -a /etc/mdadm/mdadm.conf ARRAY /dev/md1 metadata=1.2 name=fphtaeqnyi-nxwtgsavpf:1 UUID=cf674ea9:d9a5c4d9:a7e67de1:f380cf54 ``` 3. Update the “*initramfs*”. This command updates the initial RAM filesystem to include the new RAID configuration: ```bash command sudo update-initramfs -u ``` This returns: ```bash output root@fphtaeqnyi-nxwtgsavpf:~# sudo update-initramfs -u update-initramfs: Generating /boot/initrd.img-5.15.0-107-generic W: Possible missing firmware /lib/firmware/ast_dp501_fw.bin for module ast ``` 4. Assemble the RAID Array. This command ensures that the RAID array is correctly assembled on system startup: ```bash command sudo mdadm --assemble --scan ``` ### Step 5: Create a Filesystem on the RAID Array 1. Create a filesystem on the RAID array (e.g., ext4). Use this command and replace “*/dev/mdX*” with your RAID array device name: ```bash command sudo mkfs.ext4 /dev/mdX ``` You should see: ```bash output root@fphtaeqnyi-nxwtgsavpf:~# sudo mkfs.ext4 /dev/md1 mke2fs 1.46.5 (30-Dec-2021) Discarding device blocks: done Creating filesystem with 937651536 4k blocks and 234414080 inodes Filesystem UUID: 0311e850-c233-42c9-b180-74958a4a413d Superblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968, 102400000, 214990848, 512000000, 550731776, 64492544 Allocating group tables: done Writing inode tables: done Creating journal (262144 blocks): done Writing superblocks and filesystem accounting information: done ``` ### Step 6: Mount the RAID Array 1. Create a mount point with the following command, replacing “*/mnt/mdX*” with your desired mount point: ```bash command sudo mkdir -p /mnt/mdX ``` 2. To mount the RAID array, run this command, and replace “*/dev/mdX*” with your RAID array device name, and “*/mnt/mdX*” with your mount point: ```bash command sudo mount /dev/mdX /mnt/mdX ``` 3. Edit the “*/etc/fstab*” file. Open the “*/etc/fstab*” file in a text editor to ensure the RAID array persists through reboots, using: ```bash command sudo nano /etc/fstab ``` 4. Add an entry to “*/etc/fstab*”. At the bottom of the “*/etc/fstab*” file, add the following line, replacing “*/dev/mdX*” with your RAID array device name, “*/mnt/mdX*” with your mount point, and “**” with your created filesystem type: ```text /dev/mdX /mnt/mdX defaults 0 2 ``` It should look like this: ```text GNU nano 6.2 /etc/fstab * /etc/fstab: static file system information. Use 'blkid' to print the universally unique identifier for a device; this may be used with UUID= as a more robust way to name devices that works even if disks are added and removed. See fstab(5). was on /dev/md0 during curtin installation #/dev/disk/by-id/md-uuid-b264bbd4-5581775e:bf63febe:d6f5d2f2 / ext4 defaults 0 1 was on /dev/nvme0n1p1 during curtin installation #/dev/disk/by-id/DFE-6AA7 /boot/efi vfat defaults 0 1 /swap.img none swap sw 0 0 /dev/md1 /mnt/md1 ext4 defaults 0 2 ``` 5. Save and exit the editor. - Press Ctrl + X to exit. - Press Y to confirm you want to save the changes. - Press Enter to finalize the save. ### Step 7: Verify the RAID Array 1. Check the status of the RAID array using this command, and replacing “*/dev/mdX*” with your RAID array device name. ```bash command sudo mdadm --detail /dev/mdX ``` This should provide the following: ```bash output root@fphtaeqnyi-nxwtgsavpf:/# sudo mdadm --detail /dev/md1 /dev/md1: Version : 1.2 Creation Time : Tue Jun 18 22:40:49 2024 Raid Level : raid1 Array Size : 3750606144 (3.49 TiB 3.84 TB) Used Dev Size : 3750606144 (3.49 TiB 3.84 TB) Raid Devices : 2 Total Devices : 2 Persistence : Superblock is persistent Intent Bitmap : Internal Update Time : Tue Jun 18 23:44:52 2024 State : clean, resyncing Active Devices : 2 Working Devices : 2 Failed Devices : 0 Spare Devices : 0 Consistency Policy : bitmap Resync Status : 20% complete Name : fphtaeqnyi-nxwtgsavpf:1 (local to host fphtaeqnyi-nxwtgsavpf) UUID : cf674ea9:d9a5c4d9:a7e67de1:f380cf54 Events : 718 Number Major Minor RaidDevice State 0 259 5 0 active sync /dev/nvme2n1 1 259 6 1 active sync /dev/nvme3n1 ``` All steps to create a separate RAID array using two drives, while still leaving your existing RAID array untouched, have now been completed, and you may now continue operations as normal.