[Lustre-discuss] fsck of OST problems - endless loop restarting pass 1

[Craig Prescott]

Andreas Dilger wrote:
> On 2009-12-01, at 19:01, Craig Prescott wrote:
>> Andreas Dilger wrote:
>>> I would start by simply trying to mount the OST filesystem with 
>>> ldiskfs directly (mount options "-o ro" to avoid any further 
>>> corruption or errors, and possibly also "noload" to avoid recovering 
>>> the journal), and seeing if you can copy out the data from the 
>>> filesystem into a backup filesystem, and then just reformat the OST.
>>
>> Unfortunately, this did not work:
>>
>> [root at tebow2 ~]# mount -t ldiskfs -o ro /dev/F3P1L0/T2-F3P1L0 /mnt
>> mount: wrong fs type, bad option, bad superblock on 
>> /dev/F3P1L0/T2-F3P1L0,
>>       missing codepage or other error
>>       In some cases useful info is found in syslog - try
>>       dmesg | tail  or so
>>
>> In dmesg I see this:
>>
>> LDISKFS-fs error (device dm-7): ldiskfs_check_descriptors: Checksum 
>> for group 256 failed (18306!=0)
>> LDISKFS-fs: group descriptors corrupted!
> 
> You may want to disable the group descriptor checksums with:
> 
> debugfs -R "feature ^uninit_bg" {dev}
> 
> and then retry the mount and/or e2fsck.  This feature is making it more 
> difficult to use the backup descriptors for some reason.

The debugfs command didn't take - uninit_bg still showed up in 
"filesystem features" if I ran 'stats' under debugfs interactively.

But 'tune2fs -O ^uninit_bg /dev/F3P1L0/T2-F3P1L0' did work.

Unfortunately, mounting the device as ldiskfs still didn't work; from 
the syslog:

LDISKFS-fs error (device dm-7): ldiskfs_check_descriptors: Checksum for 
group 0 failed (0!=29388)

LDISKFS-fs: group descriptors corrupted!

Note that the group descriptor checksum inequality message in the syslog 
is changed - (0!=29388) is what we get now, versus (18306!=0) when group 
descriptor checksums were enabled.

I still haven't had any luck with fsck.

Do you have any other ideas?

Thanks,
Craig Prescott
UF HPC Center