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Re: Odd error: Physical size does not match superblock size



On Apr 17, 2003  14:12 -0400, Bobbyjoe Glover wrote:
> This system has two IDE disks, partitioned identically, and the largest
> partition on each (/dev/hda3 and /dev/hdb3, 96GB each) was mirrored in a
> linux software RAID-1 configuration.
> It was running fine for many months. Then I updated the kernel and
> needed to reboot accordingly. (2.4.18-14.8.0smp -> 2.4.18-27.8.0smp)

Possibly more than 6 months with only a handful of reboots?  If so, then
the reboot was the first time you actually ran e2fsck on it.

> Upon a reboot, fsck complained that /first1 (/dev/hda3)'s superblock or
> partition table reported 25712032 blocks, while the physical disk
> reported 25712016. (a difference of 16). I tested with new and old
> kernel, and the error occured on both.

The 16 blocks are the size of the MD RAID superblock (64kB)...

> Since I had the data backed up, I eventually formatted /dev/hda3 and put
> a new, clean ext3 fs on it. I then ran resize2fs and decreased the
> filesystem by 16 to match what the physical said. Then I rebuilt the
> RAID-1 array and the problem went away.

The problem is that you are creating the filesystem on /dev/hda3 and not
/dev/md0 (which is smaller by those 16 blocks because of the RAID superblock
at the end).

> I was hoping there would be a more elegant solution. Anybody have an
> idea how this error occured, or what I could have done differently?

Proper fix (if you have gotten yourseld into this problem already) is
to just use resize2fs to shrink the filesystem on /dev/md0 by 16 blocks.
Chances are that nothing is using those blocks anyways, so you are safe
(and if yes, then e2fsck will complain and fix it).

Cheers, Andreas
--
Andreas Dilger
http://sourceforge.net/projects/ext2resize/
http://www-mddsp.enel.ucalgary.ca/People/adilger/





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