We recently had some trouble with a software raid (raid1 in this case) that was set up with mdadm. Dmesg showed that the drive had errors and so we replaced it. After the disk was replaced the other disk also started reporting errors and fsck would tell us that the superblock was fucked up and couldnt be read.
First thing we did was to dd the broken disk to the new one using ddrescue .
We tried rebuilding it by finding backup superblocks :
mke2fs -n /dev/sdb1 # lists superblocks
e2fsck -b number_from_output_above /dev/sdb1
While the above works in many cases, it didnt help us. All the superblocks where gone.
Thankfully we came across a tool named TestDisk that let us view and copy the data from the disk. Check it out, it’s awesome 