RAID 1 = mirrored pair of two hard disks If one disk fail, the raid will continue to be operational. Read performance will be increased for parallel read operations. Write performance will be likely the same (almost the same).

• Two hard disks of same size.
• mdadm should be installed.

yum install mdadm

Format first hard disk (/dev/sda) with xfs (supports also hard disks higher than 2TB)

mkfs.xfs -f -L DISK1 /dev/sda

-f = force
-L = hdd label

Format second hard disk (/dev/sdb) with xfs.

mkfs.xfs -f -L DISK2 /dev/sdb

Create the raid array.

mdadm --verbose --create /dev/md0 --level=raid1 --raid-devices=2 /dev/sda /dev/sdb

Format the raid array as xfs.

mkfs.xfs /dev/md0

Mount the raid array (in /data1 folder)

mkdir /data1

mount /dev/md0 /data1

Automatically mount the raid volume at startup.
Edit /etc/fstab and add:

/dev/md0 /data1 xfs defaults 0 0

Load automatically the raid 1 configuration at startup.

mdadm --detail --scan --verbose >> /etc/mdadm.conf

Check the raid configuration.

mdadm -D /dev/md0

<code> /dev/md0:

         Version : 1.2
   Creation Time : Mon Apr 13 03:07:50 2020
      Raid Level : raid1
      Array Size : 3906886464 (3725.90 GiB 4000.65 GB)
   Used Dev Size : 3906886464 (3725.90 GiB 4000.65 GB)
    Raid Devices : 2
   Total Devices : 2
     Persistence : Superblock is persistent

   Intent Bitmap : Internal

     Update Time : Mon Apr 13 15:24:47 2020
           State : clean, resyncing
  Active Devices : 2
 Working Devices : 2
  Failed Devices : 0
   Spare Devices : 0

Consistency Policy : bitmap

   Resync Status : 90% complete

            Name : medjavaro:0  (local to host medjavaro)
            UUID : 257d9837:5eda9e27:59a51c12:d139b615
          Events : 15822

  Number   Major   Minor   RaidDevice State
     0       8       16        0      active sync   /dev/sda
     1       8       32        1      active sync   /dev/sdb

<code>