Re: How to fix bad superblock or xfs_repair: error - read only 0 of 512 bytes

[Eric Sandeen <sandeen@sandeen.net>]

On 1/24/12 9:52 AM, Christian Kildau wrote:
> On Jan 24, 2012, at 4:50 PM, Eric Sandeen wrote:
> 
>> On 1/24/12 9:46 AM, Christian Kildau wrote:
>>>
>>> On Jan 24, 2012, at 3:12 PM, Roger Willcocks wrote:
>>>
>>>>
>>>> On Tue, 2012-01-24 at 11:13 +0100, Christian Kildau wrote:
>>>>> Top posting... sorry.
>>>>>
>>>>> I have now found dozens of other users with a similar issue! e.g.
>>>>> http://www.linuxquestions.org/questions/linux-general-1/cannot-mount-hard-disk-block-count-exceeds-size-of-device-bad-partition-table-880149/
>>>>>
>>>>> To make it short all of these users were running ext4 and a fs resize to the new geometry fixed their problems! Sadly XFS doesn't support shrinking the fs(?).
>>>>>
>>>>
>>>> It seems fairly clear that your drive or the bios is lying about its
>>>> capacity. The filesystem occupies the entire disk, but the disk has
>>>> become 'smaller'. A quick web search suggests a 'hidden protected area'
>>>> - the two block counts in this link line up with the before and after
>>>> sizes you're seeing:
>>>>
>>>> http://lime-technology.com/forum/index.php?topic=13440.0;wap2
>>>>
>>>> It would be instructive to see what 'hdparm -N /dev/sdd' says on your
>>>> system. And a dmesg log would be handy too.
>>>>
>>>> Note that this is /not/ a problem with xfs. The right fix is to tell the
>>>> drive to report its actual capacity, not to shrink the filesystem.
>>>
>>> I do understand that is definitely not an XFS issue, but some strange issue with ubuntu or their kernel patches...
>>>
>>> I got my data back by dumping the entire hdd (it was partitionless nevertheless) to a bigger 2TB hdd.
>>> XFS mounts without any problems and I can restore my data.
>>>
>>> Thanks all for your help!
>>
>> It's likely still missing the end of the filesystem, though.
>>
>> Can you run the hdparm command Roger suggested on your original hard drive, please?
> 
> Sure, here it is:
> 
> /dev/sde:
>  max sectors   = 2930275055/2930277168, HPA is enabled
                                          ^^^^^^^^^^^^^^

ding ding ding, we have a winner.

2930277168-2930275055 = 2113 which is about how much xfs tried to read past the end.

Something about the ubuntu upgrade messed with your disk.

I'd press them very hard to investigate & resolve that.  You can probably use hdparm
to remove the HPA and get your space back but this is beyond my expertise &
familiarity.  It'd be interesting to know what is _in_ the HPA area first.

-Eric

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