raid 5 array missing after 1 disk error

Hi everybody !

i had trouble to rebuild my raid 5 after a mistake from mine on the nas

just for a quick explanation : i have a omv vm into proxmox, one time i did install a windows into another ssd without unplugging my 3 hdd used into my omv raid 5

the installation create a ntfs partition on sdb then my raid was **** up, my fault.

what i did : i detached sdb to recover some data but there is no more access to file system,

i reformate the sdb disk, allowed it to omv again but on raid menu only sdb is available, the two other seems not available even if they can be still seen on disk menu

i think it's just stupid configuration missing somewhere or command to do but i don't want to play with fire without any advices

disk : ironwolf red 4tb x3

for some command i found here is

thx for any help !

cat /proc/mdstat

Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : inactive sdc[1](S) sdd[2](S)
      7813724160 blocks super 1.2

blkid

/dev/sr0: BLOCK_SIZE="2048" UUID="2023-07-24-10-07-42-00" LABEL="openmediavault 20230724-12:07" TYPE="iso9660" PTUUID="fb4aed61" PTTYPE="dos"
/dev/sda1: UUID="0b0cb9fb-ebc6-48d2-941d-1da1c8bd8a06" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="c5600119-01"
/dev/sda5: UUID="46897158-dd1a-4ec1-a81d-5608b0ceb88d" TYPE="swap" PARTUUID="c5600119-05"
/dev/sdc: UUID="584d7feb-b031-c2e3-14b2-b2b17e730d84" UUID_SUB="7c90c282-d65f-11ea-6654-ed665c55059a" LABEL="OMVNAS:0" TYPE="linux_raid_member"
/dev/sdd: UUID="584d7feb-b031-c2e3-14b2-b2b17e730d84" UUID_SUB="cc9915a5-0581-aac8-8864-397bfdac9391" LABEL="OMVNAS:0" TYPE="linux_raid_member"

fdisk -l | grep "Disk "

Disk /dev/sda: 32 GiB, 34359738368 bytes, 67108864 sectors
Disk model: QEMU HARDDISK
Disk identifier: 0xc5600119
Disk /dev/sdb: 3,64 TiB, 4000762036224 bytes, 7813988352 sectors
Disk model: QEMU HARDDISK
Disk /dev/sdc: 3,64 TiB, 4000762036224 bytes, 7813988352 sectors
Disk model: QEMU HARDDISK
Disk /dev/sdd: 3,64 TiB, 4000762036224 bytes, 7813988352 sectors
Disk model: QEMU HARDDISK

cat /etc/mdadm/mdadm.conf

# This file is auto-generated by openmediavault (https://www.openmediavault.org)
# WARNING: Do not edit this file, your changes will get lost.

# mdadm.conf
#
# Please refer to mdadm.conf(5) for information about this file.
#

# by default, scan all partitions (/proc/partitions) for MD superblocks.
# alternatively, specify devices to scan, using wildcards if desired.
# Note, if no DEVICE line is present, then "DEVICE partitions" is assumed.
# To avoid the auto-assembly of RAID devices a pattern that CAN'T match is
# used if no RAID devices are configured.
DEVICE partitions

# auto-create devices with Debian standard permissions
CREATE owner=root group=disk mode=0660 auto=yes

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

# definitions of existing MD arrays
ARRAY /dev/md0 metadata=1.2 name=OMVNAS:0 UUID=584d7feb:b031c2e3:14b2b2b1:7e730d84

mdadm --detail --scan --verbose

INACTIVE-ARRAY /dev/md0 num-devices=2 metadata=1.2 name=OMVNAS:0 UUID=584d7feb:b031c2e3:14b2b2b1:7e730d84
   devices=/dev/sdc,/dev/sdd

mdadm --examine /dev/sdb

mdadm: No md superblock detected on /dev/sdb.

Hey !
a little bit disappointed that there is no answers after 3 months, but lets forget it
i someone pass by with the same problem, you should unmount and re mount the raid manually by adding the hdd missing

here is what i have done (adapt sda/sdb/... depending on your setup)mdadm --stop /dev/md0 (stop the raid)
mdadm --assemble --force /dev/md0 /dev/sdc /dev/sdd (sdc and sdd are the 2 hdd intact for me, you should see a msg saying it started assembling)
then check time to time until finished with cat /proc/mdstat
assemble system files :

mkdir -p /mnt/raid
mount /dev/md0 /mnt/raid

auto mount raid
UUID=<UUID> /mnt/raid ext4 defaults,nofail,relatime 0 2

<UUID> => your UUID from blkid /dev/md0
and then it was ok for me, enjoy and backup !