RAID - mdadm - Check the RAID status

cat /proc/mdstat

returns:

Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4] [multipath] 
md0 : active raid6 sdf3[0] sdd3[7] sdg3[6] sdh3[5] sdc3[4] sdb3[2] sda3[3] sde3[1]
      46824429696 blocks super 1.0 level 6, 64k chunk, algorithm 2 [8/8] [UUUUUUUU]
      bitmap: 21/59 pages [84KB], 65536KB chunk

NOTE:

Personalities: What RAID levels the kernel currently supports.
- This can be changed by either changing the raid modules or recompiling the kernel.
- Possible personalities include: [raid0] [raid1] [raid4] [raid5] [raid6] [linear] [multipath] [faulty]
  - [faulty] is a diagnostic personality; it does not mean there is a problem with the array.

md0: The device is /dev/md0.
active: The RAID is active and started.
- An inactive array is usually faulty. Stopped arrays are not visible here.
raid6: The type of RAID array and the component devices are:
- sdf3[0] is device 0.
- sdd3[7] is device 7.
- sdg3[6] is device 6.
- sdh3[5] is device 5.
- sdc3[4] is device 4.
- sdb3[2] is device 2.
- sda3[3] is device 3.
- sde3[1] is device 1.
  - The order in which the devices appear in this line means nothing.
46824429696 blocks: The usable size of the array in blocks.
super 1.0: The array uses a 1.0 superblock.
level 6: Confirms this is a level 6 array.
64k chunk: Has a chunk size of 64k.
- This is the size for 'chunks' and is only relevant to raid levels that involve striping (1,4,5,6,10).
- The address space of the array is conceptually divided into chunks and consecutive chunks are striped onto neighboring devices.
algorithm 2: Uses algorithm 2.
[8/8]: The first number is the number of a complete raid devices as defined. The second number is how many devices are in use.
[UUUUUUUU]: The status of each device.
- F: The drive has failed.
- U: The drive is used and working fine.
- _: The drive is down.

mdadm --detail /dev/md1

returns:

/dev/md1:
        Version : 1.0
  Creation Time : Tue Mar  6 17:46:54 2018
     Raid Level : raid6
     Array Size : 46824429696 (44655.26 GiB 47948.22 GB)
  Used Dev Size : 7804071616 (7442.54 GiB 7991.37 GB)
   Raid Devices : 8
  Total Devices : 8
    Persistence : Superblock is persistent
 
  Intent Bitmap : Internal
 
    Update Time : Tue Sep 14 00:02:02 2021
          State : active 
 Active Devices : 8
Working Devices : 8
 Failed Devices : 0
  Spare Devices : 0
 
         Layout : left-symmetric
     Chunk Size : 64K
 
           Name : 1
           UUID : 85d45e53:913fde8a:55ba7e06:ee932838
         Events : 16304341
 
    Number   Major   Minor   RaidDevice State
       0       8       83        0      active sync   /dev/sdf3
       1       8       67        1      active sync   /dev/sde3
       3       8        3        2      active sync   /dev/sda3
       2       8       19        3      active sync   /dev/sdb3
       4       8       35        4      active sync   /dev/sdc3
       5       8      115        5      active sync   /dev/sdh3
       6       8       99        6      active sync   /dev/sdg3
       7       8       51        7      active sync   /dev/sdd3