How To Recover From Creating >2TB ext3 Filesystem on MSDOS Partition Table?

[Ling C. Ho]

Can u recreate your sdb1 using parted, but specifying a different end 
size, or just use "-1" ? And maybe try changing the label to "gpt" ? 
Then run e2fsck -n and see what it does. I wonder how you were able to 
create a 4TB ext3 filesystem with the msdos label under SL4.3. Never 
worked for me without the labelling it gpt.

Jon Forrest wrote:
> (I've already sent this message to Ted Ts'o directly. I should
> have sent it to this list first but I didn't know about it
> until today. My apologies to Ted.)
>
> Last Friday a system that I just inherited refused to mount
> a file system that had been working fine for about 6 months.
> This is on a Scientific Linux 4.3 system using a 2.6.9
> kernel. This is another Linux distribution based on RHEL 4.
> I don't think the actual hardware is relevant
> here so I won't mention it. If there's more information you'd
> like to see I'd be happy to provide it.
>
> It turns out that this 4.2TB file system was created in an
> msdos partition table, as shown below:
>
> ----
> GNU Parted 1.6.19
> Using /dev/sdb
> (parted) p
> Disk geometry for /dev/sdb: 0.000-4291443.000 megabytes
> Disk label type: msdos
> Minor    Start       End     Type      Filesystem  Flags
> 1          0.031  97137.567  primary   ext3
> ----
>
> Running fsck fails as shown below:
>
> ----
> e2fsck 1.35 (28-Feb-2004)
> The filesystem size (according to the superblock) is 1098609033 blocks
> The physical size of the device is 24867209 blocks
> Either the superblock or the partition table is likely to be corrupt!
> Abort<y>? yes
>
> Error reading block 24870914 (Invalid argument) while doing inode scan.
> ----
>
> I have 2 questions:
>
> 1) How did this system run just file for ~6 months using this
> file system as a /home? I'm suspecting that the problem
> actually occurred long ago when the file system allocated
> meta or user data in blocks that are somehow unreachable
> by fsck but exactly how this could have happened isn't
> clear. Although it's too late now, I'd really like
> to know what happened.
>
> 2) Given that this happened, how can I recover as many
> files as possible from this file system? The professor
> who owns this system had put his faith in hardware
> RAID so he had never backed it up. He's very nervous
> right now.
>
> Any information or help you can provide would be
> very much appreciated.
>
> Cordially,
> Jon Forrest
> Unix Computing Support
> College of Chemistry
> Univ. of Cal. Berkeley
> 173 Tan Hall
> Berkeley, CA
> 94720-1460
> 510-643-1032
> jlforrest at berkeley.edu
>
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