Hi Phil,

Thank you so much to have taken the time to write back to me.

I already tried --assemble --force, indeed and, that did not work. I
guess it can work if you have a single drive which is out of sync but in
my case, it is a mix of a drive with a problematic superblock (dmesg =
does not have a valid v1.2 superblock, not importing!) plus a drive
which is out of sync (dmesg = kicking non-fresh sdx from array!).

Here is the output of --assemble --force with double verbose :


# mdadm -vv --assemble
--force /dev/md127 /dev/sdf /dev/sdg /dev/sdh /dev/sdi
mdadm: looking for devices for /dev/md127
mdadm: /dev/sdf is busy - skipping
mdadm: /dev/sdh is busy - skipping
mdadm: /dev/sdi is busy - skipping
mdadm: Merging with already-assembled /dev/md/xyz
mdadm: /dev/sdi is identified as a member of /dev/md/xyz, slot 2.
mdadm: /dev/sdh is identified as a member of /dev/md/xyz, slot 3.
mdadm: /dev/sdf is identified as a member of /dev/md/xyz, slot 1.
mdadm: /dev/sdg is identified as a member of /dev/md/xyz, slot 0.
mdadm: /dev/sdf is already in /dev/md/xyz as 1
mdadm: /dev/sdi is already in /dev/md/xyz as 2
mdadm: /dev/sdh is already in /dev/md/xyz as 3
mdadm: failed to add /dev/sdg to /dev/md/xyz: Invalid argument
mdadm: failed to RUN_ARRAY /dev/md/xyz: Input/output error


If i stop the array (which was autostarted) and retry, similar output :


# mdadm -S /dev/md127
mdadm: stopped /dev/md127
# mdadm -vv --assemble
--force /dev/md127 /dev/sdf /dev/sdg /dev/sdh /dev/sdi
mdadm: looking for devices for /dev/md127
mdadm: /dev/sdf is identified as a member of /dev/md127, slot 1.
mdadm: /dev/sdg is identified as a member of /dev/md127, slot 0.
mdadm: /dev/sdh is identified as a member of /dev/md127, slot 3.
mdadm: /dev/sdi is identified as a member of /dev/md127, slot 2.
mdadm: added /dev/sdf to /dev/md127 as 1
mdadm: added /dev/sdi to /dev/md127 as 2
mdadm: added /dev/sdh to /dev/md127 as 3 (possibly out of date)
mdadm: failed to add /dev/sdg to /dev/md127: Invalid argument
mdadm: failed to RUN_ARRAY /dev/md127: Input/output error


Here is the relevant dmesg output :

[173174.307703]  sdf: unknown partition table
[173174.308374]  sdg: unknown partition table
[173174.308811] md: bind<sdf>
[173174.309385]  sdh: unknown partition table
[173174.309552] md: bind<sdi>
[173174.310411]  sdi: unknown partition table
[173174.310573] md: bind<sdh>
[173174.311299]  sdi: unknown partition table
[173174.311449] md: invalid superblock checksum on sdg
[173174.311450] md: sdg does not have a valid v1.2 superblock, not
importing!
[173174.311460] md: md_import_device returned -22
[173174.311482] md: kicking non-fresh sdh from array!
[173174.311498] md: unbind<sdh>
[173174.311909]  sdh: unknown partition table
[173174.338007] md: export_rdev(sdh)
[173174.338651] md/raid:md127: device sdi operational as raid disk 2
[173174.338652] md/raid:md127: device sdf operational as raid disk 1
[173174.338868] md/raid:md127: allocated 0kB
[173174.338880] md/raid:md127: not enough operational devices (2/4
failed)
[173174.338886] RAID conf printout:
[173174.338887]  --- level:5 rd:4 wd:2
[173174.338887]  disk 1, o:1, dev:sdf
[173174.338888]  disk 2, o:1, dev:sdi
[173174.339013] md/raid:md127: failed to run raid set.
[173174.339014] md: pers->run() failed ...



Thanks again,

Tony

On Thu, 2014-11-13 at 17:56 -0500, Phil Turmel wrote:

On 11/12/2014 10:58 AM, DeadManMoving wrote:

quoted

Hi list,

I have a failed RAID 5 array, composed of 4 x 2TB drives without hot
spare. On the fail array, it looks like there is one drive out of sync
(the one with a lower Events counts) and another drive with a missing or
corrupted superblock (dmesg is reporting "does not have a valid v1.2
superblock, not importing!" and i have a : Checksum : 5608a55a -
expected 4108a55a).

All drives seems good though, the problem was probably triggered by a a
broken communication between the external eSATA expansion card and
external drive enclosure (card, cable or backplane in the enclosure i
guess...).

I am now in the process of making exact copies of the drives with dd to
other drives.

I have an idea on how to try to get my data back but i would be happy if
someone could help/validate with the steps i intent to follow to get
there.

--create is almost always a bad idea.

Just use "mdadm -vv --assemble --force /dev/mdX /dev/sd[abcd]"

One drive will be left behind (the bad superblock), but the stale one
will be revived and you'll be able to start.

If that doesn't work, show the output of the above command.  Do NOT do
an mdadm --create.

Phil

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