Loss of data when trying to fix ext4 "group descriptors corrupted!"

Question

When I try to mount an existing disk, I get the message

sudo mount -t ext4  /dev/sdc1 /data
mount: wrong fs type, bad option, bad superblock on /dev/sdc1,
       missing codepage or helper program, or other error
       In some cases useful info is found in syslog - try
       dmesg | tail  or so

When I look at the dmesg, I get

[  707.504050] EXT4-fs (sdc1): group descriptors corrupted!

Then I run the command

sudo e2fsck -p /dev/sdc1


cloudimg-rootfs: Superblock has an invalid journal (inode 8).
CLEARED.
*** ext3 journal has been deleted - filesystem is now ext2 only ***

cloudimg-rootfs: One or more block group descriptor checksums are invalid.  FIXED.
cloudimg-rootfs: Group descriptor 0 checksum is invalid.  

cloudimg-rootfs: UNEXPECTED INCONSISTENCY; RUN fsck MANUALLY.
    (i.e., without -a or -p options)

sudo fsck.ext4 -v /dev/sdc1

One or more block group descriptor checksums are invalid.  Fix<y>? yes

Group descriptor 0 checksum is invalid.  FIXED.
Group descriptor 1 checksum is invalid.  FIXED.
Group descriptor 2 checksum is invalid.  FIXED.
Group descriptor 3 checksum is invalid.  FIXED.
Group descriptor 4 checksum is invalid.  FIXED.
Group descriptor 5 checksum is invalid.  FIXED.
Group descriptor 6 checksum is invalid.  FIXED.
Group descriptor 7 checksum is invalid.  FIXED.
Group descriptor 8 checksum is invalid.  FIXED.
Group descriptor 9 checksum is invalid.  FIXED.
Group descriptor 10 checksum is invalid.  FIXED.
Group descriptor 11 checksum is invalid.  FIXED.
Group descriptor 12 checksum is invalid.  FIXED.
Group descriptor 13 checksum is invalid.  FIXED.
Group descriptor 14 checksum is invalid.  FIXED.
Group descriptor 15 checksum is invalid.  FIXED.
Group descriptor 16 checksum is invalid.  FIXED.
Group descriptor 17 checksum is invalid.  FIXED.
..SKIPPED..

    cloudimg-rootfs contains a file system with errors, check forced.
Resize inode not valid.  Recreate<y>? yes

Pass 1: Checking inodes, blocks, and sizes
Journal inode is not in use, but contains data.  Clear<y>? yes

Pass 2: Checking directory structure
Entry 'backup' in / (2) has invalid inode #: 3932162.
Clear<y>? yes

Entry 'conf' in / (2) has invalid inode #: 3932163.
Clear<y>? yes

Entry 'data' in / (2) has invalid inode #: 3932164.
Clear<y>? yes

Entry 'init' in / (2) has invalid inode #: 3932165.
Clear<y>? yes

Entry 'lib' in / (2) has invalid inode #: 3932166.
Clear<y>? yes

Entry 'log' in / (2) has invalid inode #: 3932167.
Clear<y>? yes

Entry 'script' in / (2) has invalid inode #: 3932168.
Clear<y>? yes

Entry 'site' in / (2) has invalid inode #: 3932169.
Clear<y>? yes

Entry 'tmp' in / (2) has invalid inode #: 3932170.
Clear<y>? yes

Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Inode 2 ref count is 12, should be 3.  Fix<y>? yes

Pass 5: Checking group summary information
Block bitmap differences:  -(89--601) -(603--1024) -9254 -(32857--33792) -(34816--98303) -(98393--99328) -(100352--163839) -(163929--164864) -(165888--229375) -(229465--230400) -(231424--294911) -(295001--295936) -(296960--524287) -(557056--819199) -(819289--820224) -(821248--884735) -(884825--885760) -(886784--1048575) -(1081344--1572863) -(1605721--1606656) -(1607680--1641853) -(1641984--1658367) -(1658880--1702655) -(1702912--1726975) -(1727488--1738239) -(1738752--1991679) -(1992704--2055679) -(2056192--2061567) -(2062336--2082303) -(2082816--2097151) -(2129920--2452991) -(2453504--2480383) -(2482176--2517503) -(2519040--2580735) -(2580992--2581503) -(2582528--2621439) -(2654297--2655232) -(2656256--2713343) -(2713600--2723327) -(2723840--2735103) -(2736128--2743295) -(2744320--2745855) -(2746368--2760447) -(2760704--2765567) -(2766848--2804991) -(2805760--2837503) -(2838528--2842367) -(2842624--2893055) -(2893312--2909439) -(2910208--3013631) -(3014656--3145727) -(3178496--3417343) -(3417600--3437055) -(3438592--3442175) -(3442688--3454463) -(3454976--3670015) -(3702784--3775743) -(3776000--3897599) -(3899392--3902207) -(3902464--3922687) -(3923968--3937279) -(3938304--3993855) -(3995648--4011775) -(4012032--4043519) -(4043776--4044287) -(4044800--4065023) -(4065280--4068863) -(4069376--4074495) -(4075520--4089599) -(4089856--4095999) -(4096089--4099840) -(4100096--4119295) -(4120576--4124415) -(4124672--4179199) -(4179968--4185599) -(4186112--4192511) -(4193280--4194303) -(4227072--4229375) -(4230144--4273407) -(4274176--4301567) -(4301824--4318207) -(4319232--4380927) -(4381184--4381695) -(4382720--4426495) -(4426752--4460031) -(4460544--4563455) -(4563968--4625919) -(4626432--4718591) -(4751360--4840191) -(4841472--4862463) -(4862976--4878079) -(4878336--5086463) -(5086720--5110783) -(5111808--5158399) -(5158912--5204991) -(5206016--5218047) -(5218304--5231615) -(5232640--5242879) -(5275648--5383167) -(5384192--5451519) -(5451776--5457407) -(5457920--5471231) -(5472256--5474815) -(5476352--5484031) -(5484544--5512235) -(5513216--5583359) -(5583872--5670143) -(5670400--5685759) -(5686272--5703423) -(5703680--5750015) -(5750784--5767167) -(5799936--5892863) -(5893120--5906175) -(5906432--5946367) -(5947392--5964031) -(5965824--6018815) -(6019072--6034687) -(6035456--6093311) -(6094848--6097919) -(6098944--6291455) -(6324224--6378239) -(6379520--6409215) -(6410240--6429695) -(6430720--6558207) -(6559744--6702079) -(6703104--6740991) -(6742016--6815743) -(6848512--6929919) -(6930432--7140095) -(7141376--7144959) -(7145472--7149055) -(7149568--7156991) -(7157760--7161599) -(7161856--7171071) -(7172096--7185919) -(7186432--7195647) -(7196672--7224063) -(7225344--7340031) -(7340043--7340047) -(7340059--7340063) -(7345696--7348255) -(7372800--7463423) -(7464960--7491071) -(7491584--7502847) -(7503872--7523839) -(7524352--75315

Fix<y>? yes

Free blocks count wrong for group #0 (23512, counted=24449).
Fix<y>? yes

Free blocks count wrong for group #1 (1023, counted=32679).
Fix<y>? yes

Free blocks count wrong for group #2 (0, counted=32768).
Fix<y>? yes
..SKIPPED..

Finally..

cloudimg-rootfs: ***** FILE SYSTEM WAS MODIFIED *****

      11 inodes used (0.00%)
       0 non-contiguous files (0.0%)
       0 non-contiguous directories (0.0%)
         # of inodes with ind/dind/tind blocks: 0/0/0
         Extent depth histogram: 2
  121775 blocks used (1.59%)
       0 bad blocks
       0 large files

       0 regular files
       2 directories
       0 character device files
       0 block device files
       0 fifos
       0 links
       0 symbolic links (0 fast symbolic links)
       0 sockets
--------
       2 files

Question: When I try to mount it again, this time is successfully, but only showing empty partition with only lost+found folder, and my 100GB partition become 29GB.

Any idea?

Solution

Your file system became hopelessly corrupt, and what little e2fsck can do to save it is not enough. Nuke the FS and restore from backups. I would add "consider replacing the hardware" except that what you post above suggests this is a virtual server.

In answer to your comment above, what you did is pretty much all of us can do in the event of a FS lunching itself (except FS kernel hackers, who might be able to use debugfs). Don't blame yourself - unless you don't have any backups, in which case do blame yourself, and learn an important lesson.

Comments

[Ryan]

@MadHatter, is my steps above incorrect or is the other reasons?

[MadHatter]

By the way, Yoga, you've asked 76 questions on SF and accepted answers to surprisingly few of the recent ones. Accepting an answer to a question rewards both you and the author of the answer, and prevents the question floating around forever like a querulous albatross. Please consider going back through your stack of old questions and accepting answers where they satisfy you.