manually create Linux software raid system

1: stop md 

mdadm --stop /dev/md124

2: zap disk

sgdisk -Z /dev/sda

3: creat partition

sgdisk -n 1::1024MiB /dev/sda

sgdisk -n 2:: /dev/sda

4: update partition information

partprobe /dev/sda

5: zero-superbolock

mdadm --zero-superblock /dev/sda1

6: create sw raid -> use metadata 1.2 for data, 0.9 for boot

echo yes| mdadm --create /dev/md127 --force --level=1 --raid-devices=2 --name=root--uuid=1f975454:e7eb215d:e5a8a80e:43d5a964 --metadata=1.2 /dev/sda2 /dev/sdb2

echo yes| mdadm --create /dev/md/boot --force --level=1 --raid-devices=2 --uuid=2fd35b47:0866ab39:7a1ebdb9:dcc7dd0f --metadata=0.90 --name=boot-efi /dev/sda1 /dev/sdb1

7: wait resync to be ready

while [ 1 ];do

  sts_resync=$(cat /proc/mdstat|grep resync|wc -l)

  if [ $sts_resync -ne 0 ];then

    echo "syncing"

  else

    echo "rsync ready"

    break

  fi

  sleep 5

done

software raid on RHEL7.5

review disk layout
parted /dev/sdx u s p

raid creation process
1: create 2x type code 0xfd partitions

2: set raid flag to all partitions
parted /dev/sdx set 1 raid on

3: set boot flag to partition which serves for grub configuration files
parted /dev/sdx set 1 boot on

4: zero out superblock

mdadm --zero-superblock /dev/sdx[1-9]

5: create raid

mdadm --create /dev/md0 --name=root -n2 -l1 /dev/sda1 /dev/sdb1

mdadm --create /dev/md0 --name=root -n2 -l1 /dev/sda2 /dev/sdb2

6: delete raid

mdadm --delete /dev/md0

mdadm --zero-superblock /dev/sdx[1-9]

mdadm --stop /dev/md0

6: repair raid

mdadm --add /dev/md0 /dev/sda1

7:scan available md

mdadm --examine --scan

mdadm --examine /dev/sdx[1-9]

8: raid uuid - this information need to be included in /etc/default/grub
mdadm --detail /dev/md0|grep UUID
rd.md.uuid=xxxx

9: activate software raid
mdadm -A -R /dev/md0 /dev/sda1 /dev/sdb1

others:
don't forget to creating new initramfs
dracut -f --mdadmconf

to install grub2 on a drive. mdadm package needs to be installed first and grub needs to be installed to whole disk drive instead of partition. grub needs to be installed on both drives
grub2-install --no-floppy --boot-directory=/boot /dev/sda