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Re: XFS: SB validate failed

To: Stefan Smietanowski <stesmi@xxxxxxxxxx>
Subject: Re: XFS: SB validate failed
From: Hamid <spam.wax@xxxxxxxxx>
Date: Sun, 01 Jun 2008 03:35:36 -0400
Cc: Timothy Shimmin <tes@xxxxxxx>, Eric Sandeen <sandeen@xxxxxxxxxxx>, xfs@xxxxxxxxxxx
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I think you have the terminology a little mixed up.

If you mount a something without supplying -o loop "mount" will assume
the filesystem resides in a DEVICE.

If you mount a something WHILE supplying -o loop you tell "mount" that
it should mount it using a loop device. Note device here, it's trickery
really as what it does is that "mount" will FIRST create a new device
node "/dev/loop0" for example and then it will mount from that device

Thanks Stefan, Now it makes real sense.

I guess I am back to my original question:
What does 'SB validate failed' indicate and what it really means to my case ?

fdisk reports the structure of the Jaz disk as:

$ sudo fdisk -ul jaz7.img

Disk jaz7.img (SGI disk label): 255 heads, 63 sectors, 0 cylinders
Units = sectors of 1 * 512 bytes

----- partitions -----
Pt#    Device  Info     Start       End   Sectors  Id  System
8: jaz7.img1            3072   2091007   2087936   a  SGI xfs
9: jaz7.img2               0      3071      3072   0  SGI volhdr
11: jaz7.img3               0   2091007   2091008   6  SGI volume
----- Bootinfo -----
Bootfile: /unix
----- Directory Entries -----
0: sgilabel   sector    3 size     512

I went ahead and tried to mount Partition 8 from image using the offset and loop options of the mount command:

$ sudo mount -t xfs -o loop,offset=$((512*3072)) jaz7-partition.img /mnt
mount: wrong fs type, bad option, bad superblock on /dev/loop1,
      missing codepage or helper program, or other error
      In some cases useful info is found in syslog - try
      dmesg | tail  or so

And system log says:

XFS: bad magic number
XFS: SB validate failed

So I am guessing I have one of these 3 cases:
1- Bad partition table, good file system
2- Good partition table, corrupt file system
3- Or both gone south!!!

I checked the man pages of 'vh' on Irix. It seems that the volhdr
partition is 'usually' 2 megabytes but the disk in question has 3072*512 bytes ?
Can this be a sign of corruption ?

So where would you start looking at if you wanted to fix this problem ?
Partition table or the file system ?

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