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

To: Christian Kildau <lists@xxxxxxxxxxxxx>
Subject: Re: How to fix bad superblock or xfs_repair: error - read only 0 of 512 bytes
From: Roger Willcocks <roger@xxxxxxxxxxxxxxxx>
Date: Tue, 24 Jan 2012 14:12:21 +0000
Cc: Eric Sandeen <sandeen@xxxxxxxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <B1F1FDAB-0D48-48FE-8FFC-F0567780E052@xxxxxxxxxxxxx>
References: <CALx8gnT9tdPRGfVR0puoSVYz_MDDs4FtWtodST5x29GDnL3A_w@xxxxxxxxxxxxxx> <20120123043117.GH15102@dastard> <92CDAC52-1BA1-43A8-8470-0E2DCD916610@xxxxxxxxxxxxx> <4F1E3BD0.7080604@xxxxxxxxxxx> <B1F1FDAB-0D48-48FE-8FFC-F0567780E052@xxxxxxxxxxxxx>
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.


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