How to enable write-intent bitmap on software RAID devices

Enable write-intent bitmap (internal) on software RAID devices (Multiple Device driver aka Linux Software RAID).

Inspect MD devices.

$  cat /proc/mdstat 

Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10] 
md0 : active raid1 sdb2[1] sda2[0]
      960806720 blocks super 1.2 [2/2] [UU]
      
md1 : active raid1 sda3[0] sdb3[1]
      15813504 blocks super 1.2 [2/2] [UU]
      
unused devices: <none>

Inspect device details.

$ sudo mdadm --detail /dev/md0

/dev/md0:
           Version : 1.2
     Creation Time : Tue May 24 17:50:17 2022
        Raid Level : raid1
        Array Size : 960806720 (916.30 GiB 983.87 GB)
     Used Dev Size : 960806720 (916.30 GiB 983.87 GB)
      Raid Devices : 2
     Total Devices : 2
       Persistence : Superblock is persistent

       Update Time : Sun May 29 20:31:58 2022
             State : clean 
    Active Devices : 2
   Working Devices : 2
    Failed Devices : 0
     Spare Devices : 0

Consistency Policy : resync

              Name : pxe-rescue:0
              UUID : bfdfd734:8476c2c5:160c8d7e:336308bf
            Events : 4745

    Number   Major   Minor   RaidDevice State
       0       8        2        0      active sync   /dev/sda2
       1       8       18        1      active sync   /dev/sdb2

$ sudo mdadm --detail /dev/md1

/dev/md1:
           Version : 1.2
     Creation Time : Tue May 24 17:50:17 2022
        Raid Level : raid1
        Array Size : 15813504 (15.08 GiB 16.19 GB)
     Used Dev Size : 15813504 (15.08 GiB 16.19 GB)
      Raid Devices : 2
     Total Devices : 2
       Persistence : Superblock is persistent

       Update Time : Sun May 29 15:40:32 2022
             State : clean 
    Active Devices : 2
   Working Devices : 2
    Failed Devices : 0
     Spare Devices : 0

Consistency Policy : resync

              Name : pxe-rescue:1
              UUID : 5d9ec27a:bfb45b7a:812cbe55:fcadf3ca
            Events : 21

    Number   Major   Minor   RaidDevice State
       0       8        3        0      active sync   /dev/sda3
       1       8       19        1      active sync   /dev/sdb3

Enable write-intent bitmap that will be stored with the metadata on the array.

$ sudo mdadm --grow --bitmap=internal /dev/md0

$ sudo mdadm --grow --bitmap=internal /dev/md1

Inspect MD devices.

$ cat /proc/mdstat 

Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10] 
md0 : active raid1 sdb2[1] sda2[0]
      960806720 blocks super 1.2 [2/2] [UU]
      bitmap: 3/8 pages [12KB], 65536KB chunk

md1 : active raid1 sda3[0] sdb3[1]
      15813504 blocks super 1.2 [2/2] [UU]
      bitmap: 0/1 pages [0KB], 65536KB chunk

unused devices: <none>

Disable write-intent bitmap on an MD device.

$ sudo mdadm --grow --bitmap=none /dev/md1

Inspect MD devices.

$ cat /proc/mdstat 

Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10] 
md0 : active raid1 sdb2[1] sda2[0]
      960806720 blocks super 1.2 [2/2] [UU]
      bitmap: 3/8 pages [12KB], 65536KB chunk

md1 : active raid1 sda3[0] sdb3[1]
      15813504 blocks super 1.2 [2/2] [UU]
      
unused devices: <none>

Inspect device details.

$ sudo mdadm --detail /dev/md0

/dev/md0:
           Version : 1.2
     Creation Time : Tue May 24 17:50:17 2022
        Raid Level : raid1
        Array Size : 960806720 (916.30 GiB 983.87 GB)
     Used Dev Size : 960806720 (916.30 GiB 983.87 GB)
      Raid Devices : 2
     Total Devices : 2
       Persistence : Superblock is persistent

     Intent Bitmap : Internal

       Update Time : Sun May 29 22:11:43 2022
             State : clean 
    Active Devices : 2
   Working Devices : 2
    Failed Devices : 0
     Spare Devices : 0

Consistency Policy : bitmap

              Name : pxe-rescue:0
              UUID : bfdfd734:8476c2c5:160c8d7e:336308bf
            Events : 4748

    Number   Major   Minor   RaidDevice State
       0       8        2        0      active sync   /dev/sda2
       1       8       18        1      active sync   /dev/sdb2

$ sudo mdadm --detail /dev/md1

/dev/md1:
           Version : 1.2
     Creation Time : Tue May 24 17:50:17 2022
        Raid Level : raid1
        Array Size : 15813504 (15.08 GiB 16.19 GB)
     Used Dev Size : 15813504 (15.08 GiB 16.19 GB)
      Raid Devices : 2
     Total Devices : 2
       Persistence : Superblock is persistent

       Update Time : Sun May 29 20:37:31 2022
             State : clean 
    Active Devices : 2
   Working Devices : 2
    Failed Devices : 0
     Spare Devices : 0

Consistency Policy : resync

              Name : pxe-rescue:1
              UUID : 5d9ec27a:bfb45b7a:812cbe55:fcadf3ca
            Events : 23

    Number   Major   Minor   RaidDevice State
       0       8        3        0      active sync   /dev/sda3
       1       8       19        1      active sync   /dev/sdb3