[case]filesystem problem
e2fsck 1.42 (29-Nov-2011) fsck.ext4: Superblock invalid, trying backup blocks... fsck.ext4: Bad magic number in super-block while trying to open /dev/sdb1
使用e2fsck进行修复即可。
http://unix.stackexchange.com/questions/33284/recovering-ext4-superblocks