RAID

Create RAID 5 Ubuntu

Disk Information

lsblk -o NAME,SIZE,FSTYPE,TYPE,MOUNTPOINT

NAME     SIZE FSTYPE TYPE MOUNTPOINT
sda    931.5G        disk 
└─sda1 931.5G ntfs   part /var/lib/transmission-daemon/downloads/HM_30
sdb    931.5G        disk 
└─sdb1 931.5G ntfs   part 
sdc    931.5G        disk 
└─sdc1 931.5G ntfs   part /var/lib/transmission-daemon/downloads/HM_40
sdd    931.5G        disk 
├─sdd1   100M ntfs   part 
├─sdd2   293G ntfs   part 
├─sdd3    14G ntfs   part 
├─sdd4     1K        part 
├─sdd5    28G ext4   part /
├─sdd6  93.1G ext4   part /home
├─sdd7  11.2G swap   part [SWAP]
└─sdd8   1.9G ext4   part /var/log
sdi      3.7T        disk 
sdj      3.7T        disk 
sdk      3.7T        disk 
sdl      3.7T        disk 
sr0     1024M        rom  

Disks order

/dev/sdl <-- Up
/dev/sdk
/dev/sdj
/dev/sdi <-- Down

Create RAID 5

sudo mdadm --create --verbose /dev/md0 --level=5 --raid-devices=4 /dev/sdi /dev/sdj /dev/sdk /dev/sdl

Monitor the array progress creation with

cat /proc/mdstat

Output:

Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] 
md0 : active raid5 sdl[4] sdk[2] sdj[1] sdi[0]
      11720658432 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/3] [UUU_]
      [>....................]  recovery =  0.0% (2091700/3906886144) finish=7753.1min speed=8393K/sec
      bitmap: 0/30 pages [0KB], 65536KB chunk

unused devices: <none>

https://www.digitalocean.com/community/tutorials/how-to-create-raid-arrays-with-mdadm-on-ubuntu-16-04#top
https://unix.stackexchange.com/questions/88654/what-does-mdadms-spare-number-mean
https://wiki.bandaancha.st/RAID_y_LVM_en_Linux

https://zackreed.me/software-raid-5-in-debian-with-mdadm/
https://zackreed.me/adding-an-extra-disk-to-an-mdadm-array/