I went and did a silly thing.

I had a 200 gig disk with a jfs filesystem and a duplicate (dd'd from
one to the other).  Then I decided I wanted to create a raid1 array
from the two disks, so I did the following:

  # mdadm --create /dev/md1 --auto=yes --level=1 --raid-devices=2 /dev/hdm1 
/dev/hdp1

and was subsequently able to mount and read (or seem to) the
pre-existing data, but when I rebooted, I got an error from fsck.jfs,
which I can replicate verbosely as follows:

  # fsck -v /dev/md1
  fsck 1.37 (21-Mar-2005)
  fsck.jfs version 1.1.7, 22-Jul-2004
  processing started: 5/31/2005 22.52.14

  FSCK  Device /dev/md1 is currently mounted READ ONLY.
  Using default parameter: -p
  The current device is:  /dev/md1
  Open(...READ/WRITE EXCLUSIVE...) returned rc = 0
  Incorrect jlog length detected in the superblock (P).
  Incorrect jlog length detected in the superblock (S).
  Superblock is corrupt and cannot be repaired 
  since both primary and secondary copies are corrupt.  

   CANNOT CONTINUE.

Now, I didn't really expect this to work and I have a backup of the
data, but I wonder if this is reparable in-place with the proper
jfs_debugfs incantation (or similar).  I haven't made any
modifications to the raid1 device /dev/md1 except mounting/umounting
it read/write briefly.

The /dev/md1 device is 193 sectors smaller than the underlying
partition /dev/hd?1.  Comparing the md5sums of the first 200 sectors
of /dev/md1 and /dev/hd?1, they are identical so perhaps the smaller
number of sectors is reflected at the tail.  The jfs superblock
appears to be present, it is just reporting a different fs size than
the raid1 device.

This is on a debian/testing box, with a custom-built 2.6.11.11 kernel.

Thanks for any ideas/guidance!


-- 
Russell Senior         ``I have nine fingers; you have ten.''
[EMAIL PROTECTED]


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