since this started on linux-lvm ml i'll add some missing bits
On Sat, Sep 25, 2010 at 05:31:24PM +1000, Neil Brown wrote:
....

quoted

At the moment I fixed it by modifying the /etc/mdadm/mdadm.conf file  as 
follows:

DEVICE /dev/sd[bcde]1
ARRAY /dev/md0 level=raid5 num-devices=4 
UUID=08558923:881d9efd:464c249d:988d2ec6

....

I would do
  mdadm --assemble --force --update=summaries /dev/md0 /dev/sd[abcd]1

and see if that works.

Watch it, due to drive renumbering it should be:
mdadm --assemble --force --update=summaries /dev/md0 /dev/sd[bcde]1

quoted

    * The last problem is that I believe that one of the drives has
      additional metadata. This caused Ubuntu to see an additional
      partition /dev/md0lp1 in addition to /dev/md0. What is the best
      way of removing it?

Did you mean "/dev/md0p1", or was there really an 'l' in there??

That just means that the array (/dev/md0) has a partition table.  If you want
to remove a partition table, then maybe use fdisk.

no, the problem is a little bit more complex
it seems he has duplicate metadata on each drive one for the whole drive
the other for the partition
ubuntu assembles the whole drive first, and mdadm finds the partition
table on the first disk and believe it is a partitioned md device.

L.

-- 
Luca Berra -- bluca@comedia.it
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