How to convert RAID1 to RAID0

RAID1 md volume named /dev/md2 mounted as rootfs
and two partitions named /dev/nvme0n1p4 and /dev/nvme1n1p4

We will remove second partiotion (/dev/nvme1n1p4) from raid1 members and later add it to raid0

1. Remove partition from the mirror (make it to fail state and then remove):
   # mdadm /dev/md2 -f /dev/nvme1n1p4
# mdadm /dev/md2 -r /dev/nvme1n1p4

2. Extend md2 to raid0:
   # mdadm /dev/md2 --grow --level=0

3. Add the partition of second disk back to the array md2:
   # mdadm --grow /dev/md2 --level=0 --raid-devices=2 --add /dev/nvme1n1p4
   
   Note:
   this operation will temporary change type of md2 to RAID4.
   That's okay, after reshaping md2 will back to RAID0

4. Wait for reshape to finish.

5. /dev/md2 will automatically become RAID0 after reshape is finished.

   # mdadm -D /dev/md2
   /dev/md2:
   Version : 1.2
   Creation Time : Wed Aug 3 21:48:34 2022
   Raid Level : raid0
   Array Size : 957333504 (912.98 GiB 980.31 GB)
   Raid Devices : 2
   Total Devices : 2
   Persistence : Superblock is persistent
   
   Update Time : Wed Aug 24 14:11:33 2022
   State : clean 
   Active Devices : 2
   Working Devices : 2
   Failed Devices : 0
   Spare Devices : 0
   
   Layout : -unknown-
   Chunk Size : 64K
   
   Consistency Policy : none
   
   Name : N*****1-20:2
   UUID : 14cf83f2:7e9c99e3:1114a588:18e75caa
   Events : 3373
   
   Number Major Minor RaidDevice State
   1 259 9 0 active sync /dev/nvme1n1p4
   2 259 4 1 active sync /dev/nvme0n1p4
   
   
   # cat /proc/mdstat 
   Personalities : [raid0] [raid1] [linear] [multipath] [raid6] [raid5] [raid4] [raid10] 
   md2 : active raid0 nvme0n1p4[2] nvme1n1p4[1]
   957333504 blocks super 1.2 64k chunks
   
   
   

6. Grow file system:
   # resize2fs /dev/md2
# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/md2   898G  97G  761G 12% /