Hey all,
i tried a few days to get my raid working 
tried to make array from gui and from console, but always after a reboot the raid is missing. 
Devices are 3x 4TB WD RED "WD40ERFX-68W"
Here the logs before and after reboot (logs from thread: "Degraded or missing raid array questions":
Code
root@server:~# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 sdd[2] sdc[1] sdb[0]
7813774336 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/3] [UUU]
[>....................] resync = 0.1% (6794924/3906887168) finish=431.0min speed=150807K/sec
bitmap: 30/30 pages [120KB], 65536KB chunk
unused devices: <none>
root@server:~# blkid
/dev/sda1: UUID="9dbcc7aa-8eb0-4466-b411-2007797ee89b" TYPE="ext4" PARTUUID="4410c50a-01"
/dev/sda5: UUID="718322bd-55de-4214-900c-78c0e5704a43" TYPE="swap" PARTUUID="4410c50a-05"
/dev/sdc: UUID="5edc0e86-0350-7ddc-debe-830d865ff785" UUID_SUB="ee6d94da-4d7b-c011-d914-cecc71d8f9c4" LABEL="server:raid" TYPE="linux_raid_member"
/dev/sdb: UUID="5edc0e86-0350-7ddc-debe-830d865ff785" UUID_SUB="5ca983ad-04ab-ccb7-fdde-037712cff355" LABEL="server:raid" TYPE="linux_raid_member"
/dev/sdd: UUID="5edc0e86-0350-7ddc-debe-830d865ff785" UUID_SUB="ed03741f-3b5c-3c09-feaa-afd381ee8125" LABEL="server:raid" TYPE="linux_raid_member"
root@server:~# fdisk -l | grep "Disk "
The primary GPT table is corrupt, but the backup appears OK, so that will be used.
The primary GPT table is corrupt, but the backup appears OK, so that will be used.
The primary GPT table is corrupt, but the backup appears OK, so that will be used.
Disk /dev/sdc: 3,7 TiB, 4000787030016 bytes, 7814037168 sectors
Disk identifier: FE8671E9-33B8-409A-A608-F03D3444DAF1
Disk /dev/sdb: 3,7 TiB, 4000787030016 bytes, 7814037168 sectors
Disk identifier: D75D48D8-98BE-44CC-872D-F1F2AE9C130C
Disk /dev/sda: 111,8 GiB, 120034123776 bytes, 234441648 sectors
Disk identifier: 0x4410c50a
Disk /dev/sdd: 3,7 TiB, 4000787030016 bytes, 7814037168 sectors
Disk identifier: 836F46EF-254C-4006-B7FB-F4D959912B82
Disk /dev/md0: 7,3 TiB, 8001304920064 bytes, 15627548672 sectors
root@server:~# cat /etc/mdadm/mdadm.conf
# 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=server:raid UUID=5edc0e86:03507ddc:debe830d:865ff785
root@server:~# mdadm --detail --scan --verbose
ARRAY /dev/md0 level=raid5 num-devices=3 metadata=1.2 name=server:raid UUID=5edc0e86:03507ddc:debe830d:865ff785
devices=/dev/sdb,/dev/sdc,/dev/sddCode
root@server:~# cat /proc/mdstat
Personalities :
unused devices: <none>
root@server:~# blkid
/dev/sda1: UUID="9dbcc7aa-8eb0-4466-b411-2007797ee89b" TYPE="ext4" PARTUUID="4410c50a-01"
/dev/sda5: UUID="718322bd-55de-4214-900c-78c0e5704a43" TYPE="swap" PARTUUID="4410c50a-05"
/dev/sdd: PTUUID="836f46ef-254c-4006-b7fb-f4d959912b82" PTTYPE="gpt"
/dev/sdc: PTUUID="fe8671e9-33b8-409a-a608-f03d3444daf1" PTTYPE="gpt"
/dev/sdb: PTUUID="d75d48d8-98be-44cc-872d-f1f2ae9c130c" PTTYPE="gpt"
root@server:~# fdisk -l | grep "Disk "
Disk /dev/sdd: 3,7 TiB, 4000787030016 bytes, 7814037168 sectors
Disk identifier: 836F46EF-254C-4006-B7FB-F4D959912B82
Disk /dev/sdc: 3,7 TiB, 4000787030016 bytes, 7814037168 sectors
Disk identifier: FE8671E9-33B8-409A-A608-F03D3444DAF1
Disk /dev/sdb: 3,7 TiB, 4000787030016 bytes, 7814037168 sectors
Disk identifier: D75D48D8-98BE-44CC-872D-F1F2AE9C130C
Disk /dev/sda: 111,8 GiB, 120034123776 bytes, 234441648 sectors
Disk identifier: 0x4410c50a
root@server:~# cat /etc/mdadm/mdadm.conf
# 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=server:raid UUID=5edc0e86:03507ddc:debe830d:865ff785
root@server:~# mdadm --detail --scan --verboseHope anybody can help
cyress