I accidentally overwrote all my RAID1 superblocks with garbage. I think this happened because I ALT-CTRL-DEL booted when the Ubuntu had put me in some kind of hard disk recovery mode. My display wasn't working and I did this "blind".
Looking at my RAID partitions, I see this:
# mdadm --examine /dev/sdc2
/dev/sdc2:
Magic : a92b4efc
Version : 0.90.00
UUID : 00000000:00000000:00000000:00000000
Creation Time : Fri Nov 1 18:59:05 2013
Raid Level : -unknown-
Raid Devices : 0
Total Devices : 1
Preferred Minor : 127
Update Time : Fri Nov 1 18:59:05 2013
State : active
Active Devices : 0
Working Devices : 1
Failed Devices : 0
Spare Devices : 1
Checksum : 6b1f0d22 - correct
Events : 1
Number Major Minor RaidDevice State
this 0 8 34 0 spare /dev/sdc2
0 0 8 34 0 spare /dev/sdc2
It is apparent that the superblocks have been fully overwritten by garbage. Both disks (sdb2, sdc2) look the same, the information is garbage, uuid is all zeros, raid level: unknown, raid devices: 0, etc.
The best bet I have is this:
mdadm --create --assume-clean --metadata=0.90 /dev/md0 --level=1 --raid-devices=2 /dev/sdb2 /dev/sdc2
Can I re-create my RAID array using mdadm --create like this?
On the RAID stack, I have an LVM2 physical volume. Can I somehow access my LVM2 data from the individual disks or backup disk images?
GRUB is able to find my initrd and kernel image from the disks, /boot is on ext4 root partition filesystem on top of LVM2, it is not a separate partition. So I believe the data is mostly intact, and the superblocks are gone.
edit: add --assume-clean to mdadm command line
--create
doesn't work for recovering stuff! "Yes. mdadm --create is not a recovery step. It is used to create a new, blank array, and the next step would typically be pvcreate or mkfs. Already existing arrays are started using mdadm --assemble. (This seems to be a common enough error, and has the potential to destroy data.)" unix.stackexchange.com/a/97205/41104 unix.stackexchange.com/a/96674/41104xxd
/etc. to take a look at what is actually on the drives (or images).