Comment 8 for bug 1850540

= eoan verification =

ubuntu@ip-172-30-0-147:~$ sudo mdadm --create /dev/md0 --run --metadata=default --level=0 --raid-devices=2 /dev/xvdb /dev/xvdc
mdadm: Fail create md0 when using /sys/module/md_mod/parameters/new_array
mdadm: array /dev/md0 started.
ubuntu@ip-172-30-0-147:~$ cat /proc/mdstat
Personalities : [raid0]
md0 : active raid0 xvdc[1] xvdb[0]
      3141632 blocks super 1.2 512k chunks

unused devices: <none>

# Upgraded mdadm & installed a 5.4 kernel
ubuntu@ip-172-30-0-147:~$ dmesg | grep raid
[ 3.009968] md: If you don't use raid, use raid=noautodetect
[ 5.981265] md/raid0:md0: cannot assemble multi-zone RAID0 with default_layout setting
[ 5.993787] md/raid0: please set raid0.default_layout to 1 or 2
ubuntu@ip-172-30-0-147:~$ sudo mdadm --stop /dev/md0
mdadm: stopped /dev/md0
ubuntu@ip-172-30-0-147:~$ sudo mdadm --assemble -U layout-alternate /dev/md0 /dev/xvdb /dev/xvdc
mdadm: /dev/md0 has been started with 2 drives.
ubuntu@ip-172-30-0-147:~$ cat /proc/mdstat
Personalities : [raid0]
md0 : active raid0 xvdb[0] xvdc[1]
      3141632 blocks super 1.2 512k chunks

unused devices: <none>

## reboot
ubuntu@ip-172-30-0-147:~$ dmesg | grep raid
[ 2.440539] md: If you don't use raid, use raid=noautodetect
ubuntu@ip-172-30-0-147:~$ cat /proc/mdstat
Personalities : [raid0]
md0 : active raid0 xvdb[0] xvdc[1]
      3141632 blocks super 1.2 512k chunks

unused devices: <none>
ubuntu@ip-172-30-0-147:~$ sudo mdadm --stop /dev/md0
mdadm: stopped /dev/md0
ubuntu@ip-172-30-0-147:~$ sudo mdadm --create /dev/md0 --run --metadata=default --level=0 --raid-devices=2 /dev/xvdc /dev/xvdb
mdadm: /dev/xvdc appears to be part of a raid array:
       level=raid0 devices=2 ctime=Fri Dec 6 21:30:03 2019
mdadm: /dev/xvdb appears to be part of a raid array:
       level=raid0 devices=2 ctime=Fri Dec 6 21:30:03 2019
mdadm: array /dev/md0 started.
ubuntu@ip-172-30-0-147:~$ sudo mdadm --stop /dev/md0
mdadm: stopped /dev/md0
ubuntu@ip-172-30-0-147:~$ sudo mdadm --create /dev/md0 --run --metadata=default --level=0 --raid-devices=2 /dev/xvdc /dev/xvdb --layout=original
mdadm: /dev/xvdc appears to be part of a raid array:
       level=raid0 devices=2 ctime=Fri Dec 6 21:52:42 2019
mdadm: /dev/xvdb appears to be part of a raid array:
       level=raid0 devices=2 ctime=Fri Dec 6 21:52:42 2019
mdadm: array /dev/md0 started.
ubuntu@ip-172-30-0-147:~$ sudo mdadm --detail /dev/md0 | grep Layout
            Layout : original