Well, I decided to just recreate the array and hope for the best.
mdadm --create --assume-clean --level=linear --raid-devices=2 /dev/md0 /dev/vda /dev/vdb
I put this in and rebooted the VM, and amazingly, my array was restored. All data appears to be intact. Hopefully it lasts long enough for me to copy it to another disk. 
To anyone from the future, I would only recommend this as a last resort... YMMV.
Yeah, that's what I was afraid of. I'll leave it alone for a couple of days in case anyone has any ideas, but I'm going to pull what I can off a deep scan for now.
Thanks for looking.
Yeah, my thought was to use the snapraid plugin to create a parity disk for the disks in the linear array, but I realized later that I need to use mergefs for that anyway.
For what it's worth, there was only ever maybe 4TB of data in the array to begin with, so I assume the second drive doesn't actually have anything on it.
root@openmediavault:~# mdadm --stop /dev/md0
mdadm: stopped /dev/md0
root@openmediavault:~# mdadm --assemble --force --verbose /dev/md0 /dev/vda
mdadm: looking for devices for /dev/md0
mdadm: /dev/vda is identified as a member of /dev/md0, slot 0.
mdadm: no uptodate device for slot 1 of /dev/md0
mdadm: added /dev/vda to /dev/md0 as 0
mdadm: /dev/md0 assembled from 1 drive - not enough to start the array.
root@openmediavault:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md127 : inactive vda[0](S)
7813894488 blocks super 1.2
unused devices: <none>
I was shuffling hard drives and had just reformatted my backup when this happened. Currently deep scanning it to see what I can recover, but obviously the file structure is gone on that one.
Hello,
I had a linear array with 2 drives on it... I'm not exactly sure what I did that caused it to break, but it no longer mounts at all. I'm looking for a way to either repair it or recover the data. Here's what it looks like now:
Disk 1:
root@openmediavault:~# mdadm --examine /dev/vda
/dev/vda:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x0
Array UUID : 89b4bdb7:47e966c7:bdf65f7c:0daab043
Name : openmediavault:JBOD (local to host openmediavault)
Creation Time : Sun Feb 16 12:30:43 2020
Raid Level : linear
Raid Devices : 2
Avail Dev Size : 15627788976 (7451.91 GiB 8001.43 GB)
Used Dev Size : 0
Data Offset : 264192 sectors
Super Offset : 8 sectors
Unused Space : before=264112 sectors, after=0 sectors
State : clean
Device UUID : c3018e8b:0475c41a:b3c05b7a:7fff9ebd
Update Time : Sun Feb 16 12:30:43 2020
Bad Block Log : 512 entries available at offset 8 sectors
Checksum : be74f84d - correct
Events : 0
Rounding : 0K
Device Role : Active device 0
Array State : AA ('A' == active, '.' == missing, 'R' == replacing)
Disk 2:
root@openmediavault:~# mdadm --examine /dev/vdb
mdadm: No md superblock detected on /dev/vdb.
root@openmediavault:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : inactive vda[0](S)
7813894488 blocks super 1.2
unused devices: <none>
root@openmediavault:~# blkid
/dev/sr0: UUID="2019-08-16-07-08-11-00" LABEL="openmediavault 20190816-09:05" TYPE="iso9660" PTUUID="55882e75" PTTYPE="dos"
/dev/vda: UUID="89b4bdb7-47e9-66c7-bdf6-5f7c0daab043" UUID_SUB="c3018e8b-0475-c41a-b3c0-5b7a7fff9ebd" LABEL="openmediavault:JBOD" TYPE="linux_raid_member"
/dev/sda1: UUID="3f8fadd9-9fae-424e-97bd-c0fbe0eca50a" TYPE="ext4" PARTUUID="cc273775-01"
/dev/sda5: UUID="27c2afa3-023e-4adc-823f-9f6fda5b16f3" TYPE="swap" PARTUUID="cc273775-05"
root@openmediavault:~# fdisk -l | grep "Disk "
Disk /dev/vda: 7.3 TiB, 8001563222016 bytes, 15628053168 sectors
Disk /dev/vdb: 7.3 TiB, 8001563222016 bytes, 15628053168 sectors
Disk /dev/sda: 16 GiB, 17179869184 bytes, 33554432 sectors
Disk model: QEMU HARDDISK
Disk identifier: 0xcc273775
root@openmediavault:~# cat /etc/mdadm/mdadm.conf
cat: /etc/mdadm/mdadm.conf: No such file or directory
root@openmediavault:~# mdadm --detail --scan --verbose
INACTIVE-ARRAY /dev/md0 num-devices=1 metadata=1.2 name=openmediavault:JBOD UUID=89b4bdb7:47e966c7:bdf65f7c:0daab043
devices=/dev/vda
Anything I can do to fix this?
Thanks.
