Recently I accidentally ran mkfs.ext3 on the wrong RAID1 array.
As soon as I realized what had happened, I shut power off from the PC.
Booting to a live CD, I ran
mdadm –assemble /dev/md0 /dev/sda1 /dev/sdb1
fsck -y /dev/md0
I was able to then mount the drive
mount /dev/md0 /media/md0
And the majority of my files were saved.
Check to see if your filesystem is ext2 or ext3
mount | grep md0
If it’s ext2, convert it to ext3
tune2fs -j /dev/md0
WARNING: If you choose to run fsck manually (without -y), choosing “n” to Clear? and “y” to Fix? will cause you to lose that file.