Step 1: prepare to configure RAID by checking the system

In the below example, we’re using a test Linux computer that is running Ubuntu 20.04. It has 4 x Samsung SSD hard drives models 860_EVO & 870_EVO. The intention of this exercise is to setup a RAID-10 (a pair of stripped mirrors). The output shows that sda & sdc are of the same model, while sdb & sdg are of the other model. For avoid ‘lowest common denominator’ issues, we’re ensuring that each set of stripe shall consist of similar performance drives.

# Verify whether system has the software raid package installed
kimconnect@devlinux02:~$ apt list -a mdadm
Listing... Done
mdadm/hirsute,now 4.1-10ubuntu3 amd64 [installed,automatic]

# Check the partitions
root@devlinux02:/home/kimconnect# lsblk
NAME                      MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
loop0                       7:0    0  68.8M  1 loop /snap/lxd/20037
loop1                       7:1    0  55.4M  1 loop /snap/core18/1997
loop2                       7:2    0  32.3M  1 loop /snap/snapd/11588
sda                         8:0    0 931.5G  0 disk
└─sda1                      8:1    0 931.5G  0 part
sdb                         8:16   0 931.5G  0 disk
└─sdb1                      8:17   0 931.5G  0 part
sdc                         8:32   0 931.5G  0 disk
└─sdc1                      8:33   0 931.5G  0 part
sdd                         8:48   1  29.8G  0 disk
├─sdd1                      8:49   1   512M  0 part /boot/efi
├─sdd2                      8:50   1     1G  0 part /boot
└─sdd3                      8:51   1  28.3G  0 part
  └─ubuntu--vg-ubuntu--lv 253:0    0  28.3G  0 lvm  /
sdg                         8:96   0 931.5G  0 disk
└─sdg1                      8:97   0 931.5G  0 part

# Verify disk specs
ls -lF /dev/disk/by-id/

root@devlinux02:/home/kimconnect# ls -lF /dev/disk/by-id/|grep Samsung
lrwxrwxrwx 1 root root  9 Aug 13 00:38 ata-Samsung_SSD_860_EVO_1TB_S3Z8NB0KB46308J -> ../../sdb
lrwxrwxrwx 1 root root 10 Aug 13 00:46 ata-Samsung_SSD_860_EVO_1TB_S3Z8NB0KB46308J-part1 -> ../../sdb1
lrwxrwxrwx 1 root root  9 Aug 13 00:10 ata-Samsung_SSD_860_EVO_1TB_S5B3NDFN912396N -> ../../sdg
lrwxrwxrwx 1 root root 10 Aug 13 00:46 ata-Samsung_SSD_860_EVO_1TB_S5B3NDFN912396N-part1 -> ../../sdg1
lrwxrwxrwx 1 root root  9 Aug 13 00:10 ata-Samsung_SSD_870_QVO_1TB_S5VSNG0NA05357H -> ../../sda
lrwxrwxrwx 1 root root 10 Aug 13 00:46 ata-Samsung_SSD_870_QVO_1TB_S5VSNG0NA05357H-part1 -> ../../sda1
lrwxrwxrwx 1 root root  9 Aug 13 00:38 ata-Samsung_SSD_870_QVO_1TB_S5VSNJ0NC00894D -> ../../sdc
lrwxrwxrwx 1 root root 10 Aug 13 00:46 ata-Samsung_SSD_870_QVO_1TB_S5VSNJ0NC00894D-part1 -> ../../sdc1
lrwxrwxrwx 1 root root  9 Aug 13 00:38 scsi-0ATA_Samsung_SSD_860_S3Z8NB0KB46308J -> ../../sdb
lrwxrwxrwx 1 root root 10 Aug 13 00:46 scsi-0ATA_Samsung_SSD_860_S3Z8NB0KB46308J-part1 -> ../../sdb1
lrwxrwxrwx 1 root root  9 Aug 13 00:10 scsi-0ATA_Samsung_SSD_860_S5B3NDFN912396N -> ../../sdg
lrwxrwxrwx 1 root root 10 Aug 13 00:46 scsi-0ATA_Samsung_SSD_860_S5B3NDFN912396N-part1 -> ../../sdg1
lrwxrwxrwx 1 root root  9 Aug 13 00:10 scsi-0ATA_Samsung_SSD_870_S5VSNG0NA05357H -> ../../sda
lrwxrwxrwx 1 root root 10 Aug 13 00:46 scsi-0ATA_Samsung_SSD_870_S5VSNG0NA05357H-part1 -> ../../sda1
lrwxrwxrwx 1 root root  9 Aug 13 00:38 scsi-0ATA_Samsung_SSD_870_S5VSNJ0NC00894D -> ../../sdc
lrwxrwxrwx 1 root root 10 Aug 13 00:46 scsi-0ATA_Samsung_SSD_870_S5VSNJ0NC00894D-part1 -> ../../sdc1
lrwxrwxrwx 1 root root  9 Aug 13 00:38 scsi-1ATA_Samsung_SSD_860_EVO_1TB_S3Z8NB0KB46308J -> ../../sdb
lrwxrwxrwx 1 root root 10 Aug 13 00:46 scsi-1ATA_Samsung_SSD_860_EVO_1TB_S3Z8NB0KB46308J-part1 -> ../../sdb1
lrwxrwxrwx 1 root root  9 Aug 13 00:10 scsi-1ATA_Samsung_SSD_860_EVO_1TB_S5B3NDFN912396N -> ../../sdg
lrwxrwxrwx 1 root root 10 Aug 13 00:46 scsi-1ATA_Samsung_SSD_860_EVO_1TB_S5B3NDFN912396N-part1 -> ../../sdg1
lrwxrwxrwx 1 root root  9 Aug 13 00:10 scsi-1ATA_Samsung_SSD_870_QVO_1TB_S5VSNG0NA05357H -> ../../sda
lrwxrwxrwx 1 root root 10 Aug 13 00:46 scsi-1ATA_Samsung_SSD_870_QVO_1TB_S5VSNG0NA05357H-part1 -> ../../sda1
lrwxrwxrwx 1 root root  9 Aug 13 00:38 scsi-1ATA_Samsung_SSD_870_QVO_1TB_S5VSNJ0NC00894D -> ../../sdc
lrwxrwxrwx 1 root root 10 Aug 13 00:46 scsi-1ATA_Samsung_SSD_870_QVO_1TB_S5VSNJ0NC00894D-part1 -> ../../sdc1
lrwxrwxrwx 1 root root  9 Aug 13 00:38 scsi-SATA_Samsung_SSD_860_S3Z8NB0KB46308J -> ../../sdb
lrwxrwxrwx 1 root root 10 Aug 13 00:46 scsi-SATA_Samsung_SSD_860_S3Z8NB0KB46308J-part1 -> ../../sdb1
lrwxrwxrwx 1 root root  9 Aug 13 00:10 scsi-SATA_Samsung_SSD_860_S5B3NDFN912396N -> ../../sdg
lrwxrwxrwx 1 root root 10 Aug 13 00:46 scsi-SATA_Samsung_SSD_860_S5B3NDFN912396N-part1 -> ../../sdg1
lrwxrwxrwx 1 root root  9 Aug 13 00:10 scsi-SATA_Samsung_SSD_870_S5VSNG0NA05357H -> ../../sda
lrwxrwxrwx 1 root root 10 Aug 13 00:46 scsi-SATA_Samsung_SSD_870_S5VSNG0NA05357H-part1 -> ../../sda1
lrwxrwxrwx 1 root root  9 Aug 13 00:38 scsi-SATA_Samsung_SSD_870_S5VSNJ0NC00894D -> ../../sdc
lrwxrwxrwx 1 root root 10 Aug 13 00:46 scsi-SATA_Samsung_SSD_870_S5VSNJ0NC00894D-part1 -> ../../sdc1

Step 2: Setup RAID

# Initialize disks as Raid capable
diskArray=(a b c g)
partitionType=msdos
fileSystemType=ext4

for item in "${diskArray[@]}"
do
  device=/dev/sd$item
  if grep -q $device /proc/mounts;
  then
    echo "Disk $device is currently mounted. Skipping it..."
  else
    echo "configuring $device"
    parted -a optimal -s $device mklabel $partitionType
    parted -a optimal -s $device mkpart primary $fileSystemType 0% 100%
    parted -a optimal -s $device set 1 raid on
    parted -a optimal -s $device print # display partition table
  fi
done

# Create RAID
disksCount=4
diskList=[abcg]
raidMount=/dev/md0
raidLevel=10 # options are: linear, raid0, 0, stripe, raid1, 1, mirror, raid4, 4, raid5, 5, raid6, 6, raid10, 10, multipath

# Warning: this command will destroy data on disks that have previously been members of other RAID arrays
# yes | mdadm --create $raidMount --level=$raidLevel --raid-devices=$disksCount /dev/sd$diskList\1
mdadm --create $raidMount --level=$raidLevel --raid-devices=$disksCount /dev/sd$diskList\1

Optional: Troubleshooting

# How to remove disks from RAID array
raidMount=/dev/md0
diskArray=(a b c g)
for item in "${diskArray[@]}"
do
  device=/dev/sd$item
  mdadm $raidMount -r $device
done

# How to stop the RAID array (as a prerequisite to rebuilding or re-configuring)
raidMount=/dev/md0
mdadm -S $raidMount

root@devlinux02:/home/kimconnect# mdadm -S /dev/md0
mdadm: stopped /dev/md0

# Verify the new RAID array
root@devlinux02:/home/kimconnect# lsblk
NAME                      MAJ:MIN RM   SIZE RO TYPE   MOUNTPOINT
loop0                       7:0    0  55.4M  1 loop   /snap/core18/1997
loop1                       7:1    0  61.8M  1 loop   /snap/core20/1081
loop2                       7:2    0  55.4M  1 loop   /snap/core18/2128
loop3                       7:3    0  68.3M  1 loop   /snap/lxd/21260
loop4                       7:4    0  68.8M  1 loop   /snap/lxd/20037
loop5                       7:5    0  32.3M  1 loop   /snap/snapd/12704
loop6                       7:6    0  32.3M  1 loop   /snap/snapd/11588
sda                         8:0    0 931.5G  0 disk
└─sda1                      8:1    0 931.5G  0 part
  └─md0                     9:0    0   1.8T  0 raid10
sdb                         8:16   0 931.5G  0 disk
└─sdb1                      8:17   0 931.5G  0 part
  └─md0                     9:0    0   1.8T  0 raid10
sdc                         8:32   0 931.5G  0 disk
└─sdc1                      8:33   0 931.5G  0 part
  └─md0                     9:0    0   1.8T  0 raid10
sdd                         8:48   1  29.8G  0 disk
├─sdd1                      8:49   1   512M  0 part   /boot/efi
├─sdd2                      8:50   1     1G  0 part   /boot
└─sdd3                      8:51   1  28.3G  0 part
  └─ubuntu--vg-ubuntu--lv 253:0    0  28.3G  0 lvm    /
sdg                         8:96   0 931.5G  0 disk
└─sdg1                      8:97   0 931.5G  0 part
  └─md0                     9:0    0   1.8T  0 raid10

# Show RAID status
root@devlinux02:/home/kimconnect# mdadm --detail /dev/md0
/dev/md0:
           Version : 1.2
     Creation Time : Fri Aug 13 00:46:13 2021
        Raid Level : raid10
        Array Size : 1953257472 (1862.77 GiB 2000.14 GB)
     Used Dev Size : 976628736 (931.39 GiB 1000.07 GB)
      Raid Devices : 4
     Total Devices : 4
       Persistence : Superblock is persistent

     Intent Bitmap : Internal

       Update Time : Fri Aug 13 01:05:18 2021
             State : clean, resyncing
    Active Devices : 4
   Working Devices : 4
    Failed Devices : 0
     Spare Devices : 0

            Layout : near=2
        Chunk Size : 512K

Consistency Policy : bitmap

     Resync Status : 11% complete

              Name : devlinux02:0  (local to host devlinux02)
              UUID : 3287cfe9:7a213a3f:381214bb:05564dd4
            Events : 200

    Number   Major   Minor   RaidDevice State
       0       8        1        0      active sync set-A   /dev/sda1
       1       8       17        1      active sync set-B   /dev/sdb1
       2       8       33        2      active sync set-A   /dev/sdc1
       3       8       97        3      active sync set-B   /dev/sdg1

Step 3: Partition the new RAID Array

# Create a partition (volume) on the RAID array
mkfs.ext4 /dev/md0

root@devlinux02:/home/kimconnect# mkfs.ext4 /dev/md0
mke2fs 1.45.7 (28-Jan-2021)
Discarding device blocks: done
Creating filesystem with 488314368 4k blocks and 122085376 inodes
Filesystem UUID: 29e6572f-a9f1-486a-85a5-874b7bf1ff9d
Superblock backups stored on blocks:
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
        4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968,
        102400000, 214990848

Allocating group tables: done
Writing inode tables: done
Creating journal (262144 blocks): done
Writing superblocks and filesystem accounting information: done

# Mount the volume
mount=/nfs-share
mkdir $mount
raidMount=/dev/md0
mount $raidMount $mount

# Check the mount
df -hT -P $mount

root@devlinux02:/home/kimconnect# df -hT -P $mount
Filesystem     Type  Size  Used Avail Use% Mounted on
/dev/md0       ext4  1.8T   77M  1.7T   1% /mnt/raid10

# check the running Raid config
root@devlinux02:/home/kimconnect# mdadm --detail --scan
ARRAY /dev/md0 metadata=1.2 name=devlinux02:0 UUID=3287cfe9:7a213a3f:381214bb:05564dd4

# Read the contents of persistent RAID array config
cat /etc/mdadm/mdadm.conf

# Append living config into the persistent config file
mdadm --detail --scan >> /etc/mdadm/mdadm.conf

# Update file system initialization
update-initramfs -u

# Search for the new raid mount point to retrieve it's uuid expression
root@devlinux02:~$ ls -la /dev/disk/by-uuid/
total 0
drwxr-xr-x 2 root root 120 Aug 13 03:58 .
drwxr-xr-x 7 root root 140 Aug 13 03:58 ..
lrwxrwxrwx 1 root root   9 Aug 13 03:58 29e6572f-a9f1-486a-85a5-874b7bf1ff9d -> ../../md0
lrwxrwxrwx 1 root root  10 Aug 13 03:58 322fa7a9-da0a-4d01-9b97-1d4878852f07 -> ../../dm-0
lrwxrwxrwx 1 root root  10 Aug 13 03:58 73C5-267E -> ../../sdd1
lrwxrwxrwx 1 root root  10 Aug 13 03:58 e2d8ca2f-df9b-4b6c-af98-d66e3723e459 -> ../../sdd2

# Enable mount to persist on reboots
mount=/nfs-share
fileSystemType=ext4
uuid=29e6572f-a9f1-486a-85a5-874b7bf1ff9d
echo "/dev/disk/by-uuid/$uuid $mount $fileSystemType defaults 0 1" >> /etc/fstab

The above illustration has taken into account the type of file system named ext4, instead of btrfs, xfs, zfs, etc. At the time of this writing, ext4 is the standard for most Ubuntu machines. It does yield faster transfer speed than btrfs with the down side of lacking checksum, snapshots, and other modern file system features. Still, ext4 is know for stability while the other types of fs are considered bleeding edge.

Moreover, the last step of configuring a file system on a RAID array would require a reboot to verify that the newly mounted volume would persist upon restarts.

Categories: