I have 2 Raid 0 arrays (MD0 & MD1) and I mirror those two arrays (MD2). I know this isn't the most efficient setup, nor do I care because it doesn't matter for what I'm using it for. I had to do a reinstall to fix some issues that I was having with plugins. Issue is that I lost my mirror array. MD0 and MD1 are still active, but I can't remember how to re-assemble MD2. I had to do this once before, and was able to do it without losing any data.
If I remember right it was only a few commands I typed in to get it working again, I just don't want to do something that causes the array to wipe the disks. I will be looking for a solution again and will post it if I find it before someone can answer.
/dev/md0:
Version : 1.2
Creation Time : Wed May 30 14:07:02 2018
Raid Level : raid0
Array Size : 5371653120 (5122.81 GiB 5500.57 GB)
Raid Devices : 4
Total Devices : 4
Persistence : Superblock is persistent
Update Time : Wed May 30 14:07:02 2018
State : clean
Active Devices : 4
Working Devices : 4
Failed Devices : 0
Spare Devices : 0
Chunk Size : 512K
Name : helptek-omv:0
UUID : ed9156b7:78653ac0:1d5ad2e4:c013464c
Events : 0
Number Major Minor RaidDevice State
0 8 48 0 active sync /dev/sdd
1 8 16 1 active sync /dev/sdb
2 8 96 2 active sync /dev/sdg
3 8 80 3 active sync /dev/sdf
/dev/md1:
Version : 1.2
Creation Time : Wed May 30 14:07:14 2018
Raid Level : raid0
Array Size : 5371653120 (5122.81 GiB 5500.57 GB)
Raid Devices : 4
Total Devices : 4
Persistence : Superblock is persistent
Update Time : Wed May 30 14:07:14 2018
State : clean
Active Devices : 4
Working Devices : 4
Failed Devices : 0
Spare Devices : 0
Chunk Size : 512K
Name : helptek-omv:1
UUID : 6ca14c0f:c8dfdb23:a62d00d7:288bae45
Events : 0
Number Major Minor RaidDevice State
0 8 0 0 active sync /dev/sda
1 8 32 1 active sync /dev/sdc
2 8 112 2 active sync /dev/sdh
3 8 128 3 active sync /dev/sdi
[b]cat /proc/mdstat[/b]
Personalities : [raid0]
md1 : active raid0 sda[0] sdi[3] sdh[2] sdc[1]
5371653120 blocks super 1.2 512k chunks
md0 : active raid0 sdd[0] sdf[3] sdg[2] sdb[1]
5371653120 blocks super 1.2 512k chunks