Raid array missing after reboot

While I see that there are multiple other questions that seem to be about the same (or similar) issue, none of them have a difinitive answer. Hence, I ask it again.

I am following the guide here (external, Digital Ocean), specifically the "Raid 1" guide. I follow all the steps, yet when I reboot, mdadm seems to forget about the raid array created.

When recreated, it seems fine and the data on the drive seems to persist after recreation, though mdadm needs to re-sync and build the array all over again (which takes many hours). To clarify, all I need to do to get the raid drive back is to rerun the create command and remount the array.

I followed the "Save the Array Layout" section to a tee, yet this still happens. Can anyone offer guidance on how to make the array stick around?

If anyone wants to see the output of something, just ask.

/dev/sdb/ and /dev/sdc/ are the drives I am using for the array, /dev/md0 is the array.

Output of sudo blkid after reboot:

/dev/nvme0n1: PTUUID="a2ac4afb-a9fe-4c9c-aafd-ffe2e144b803" PTTYPE="gpt"
/dev/nvme0n1p1: UUID="f9b2e155-854d-4a5d-a67e-17bd15f38289" TYPE="ext4" PARTUUID="72fd637a-3f84-4c87-a1fc-6dd4d093ee1d"
/dev/sda1: LABEL="Recovery" UUID="56FEDCF2FEDCCAFF" TYPE="ntfs" PARTLABEL="Basic data partition" PARTUUID="ba0395b4-48a6-45b1-b340-cf4bfe1d29d2"
/dev/sda2: UUID="1ADD-CEB5" TYPE="vfat" PARTLABEL="EFI system partition" PARTUUID="2024cdff-4b6f-460e-827d-7443180849e6"
/dev/sda3: PARTLABEL="Microsoft reserved partition" PARTUUID="b0475376-4a4c-4388-8c13-486587f441d9"
/dev/sda4: UUID="22D0E70AD0E6E2D1" TYPE="ntfs" PARTLABEL="Basic data partition" PARTUUID="e4d35323-a0b8-4a47-9722-193cc6cd1197"
/dev/sdb: PTUUID="aea84627-3e11-46a5-8a09-96510cae3a1a" PTTYPE="gpt"
/dev/sdc: PTUUID="76fce25c-b721-441b-b82e-b42d2d43d24b" PTTYPE="gpt"

Output of sudo blkid after re-creating raid array:

/dev/nvme0n1p1: UUID="f9b2e155-854d-4a5d-a67e-17bd15f38289" TYPE="ext4" PARTUUID="72fd637a-3f84-4c87-a1fc-6dd4d093ee1d"
/dev/sda1: LABEL="Recovery" UUID="56FEDCF2FEDCCAFF" TYPE="ntfs" PARTLABEL="Basic data partition" PARTUUID="ba0395b4-48a6-45b1-b340-cf4bfe1d29d2"
/dev/sda2: UUID="1ADD-CEB5" TYPE="vfat" PARTLABEL="EFI system partition" PARTUUID="2024cdff-4b6f-460e-827d-7443180849e6"
/dev/sda4: UUID="22D0E70AD0E6E2D1" TYPE="ntfs" PARTLABEL="Basic data partition" PARTUUID="e4d35323-a0b8-4a47-9722-193cc6cd1197"
/dev/nvme0n1: PTUUID="a2ac4afb-a9fe-4c9c-aafd-ffe2e144b803" PTTYPE="gpt"
/dev/sda3: PARTLABEL="Microsoft reserved partition" PARTUUID="b0475376-4a4c-4388-8c13-486587f441d9"
/dev/sdb: UUID="f80520f0-6304-ccc5-0ec2-bd8f6a2af079" UUID_SUB="5a38cecf-4236-db6a-d369-a53271993698" LABEL="BATTLESTAR:0" TYPE="linux_raid_member"
/dev/md0: LABEL="DataStore" UUID="c5be481b-d487-4632-8594-7b0b847f327a" TYPE="ext4"
/dev/sdc: UUID="f80520f0-6304-ccc5-0ec2-bd8f6a2af079" UUID_SUB="cd27b6f9-d6e3-1c22-8746-3f2ebb3c5eb4" LABEL="BATTLESTAR:0" TYPE="linux_raid_member"

Contents of /etc/mdadm/mdadm.conf: (I make sure to update this on every recreate to ensure the UUID is updated)

# mdadm.conf
#
# !NB! Run update-initramfs -u after updating this file.
# !NB! This will ensure that initramfs has an uptodate copy.
#
# Please refer to mdadm.conf(5) for information about this file.
#

# by default (built-in), scan all partitions (/proc/partitions) and all
# containers for MD superblocks. alternatively, specify devices to scan, using
# wildcards if desired.
#DEVICE partitions containers

# automatically tag new arrays as belonging to the local system
HOMEHOST <system>

# instruct the monitoring daemon where to send mail alerts
MAILADDR root

# definitions of existing MD arrays

# This configuration was auto-generated on Mon, 05 Mar 2018 19:04:50 -0500 by mkconf

ARRAY /dev/md0 metadata=1.2 name=BATTLESTAR:0 UUID=f80520f0:6304ccc5:0ec2bd8f:6a2af079

Allright, I figured it out, thanks to a tip from another question....

What ended up solving my problem was creating an ext4 partition on each drive, and pointing mdadm at the partitions and not the drives themselves. After that, the array was persistent after reboot.

I did not try this before this question because the other question had not marked the answer as accepted.

I know it's an old post, but I was struggling with this issue and this is my result:

My disks were "frozen" - Seagate disks. You can check, if you have same issue by entering command:

hdparm -I /dev/sdb

Which showed:

Security: 
Master password revision code = 65534
    supported
not enabled
not locked
    frozen
not expired: security count
    supported: enhanced erase

I wasn't able to change this setting. The disks worked fine with regular partitions, but when I was formatting them as linux raid, they lost they partition table and were "empty" after reboot.

I created raid on partitions, not on devices:

mdadm --create --verbose /dev/md1 --level=1 --raid-devices=2 /dev/sdb1 /dev/sdc1

And now they are fine after reboot and everything works as expected.