On 08/08/11 16:34, NeilBrown wrote:

When there have been no writes for a little while, mdmon will notice and mark
the array as 'clean'.  It will then mark it 'dirty' before the first write is
allowed to proceed.
On a clean shutdown of the array it will mark that array as 'clean'.

But for you, the system shuts down with the array marked 'dirty'.  This
suggests that on your machine 'mdmon' is being killed while the array is
still active.

Presumably your root is on the IMSM RAID10 array?  When the root filesystem
is marked 'read only' it will probably write to the filesystem to record that
a fsck is not needed.  So the array will be 'dirty'.  If you then halt before
mdmon has a chance to mark the array 'clean' you will get exactly the result
you see.

If you arrange that the shutdown script runs
  mdadm --wait-clean --scan

after marking the root filesystem readonly, it will wait until all arrays are
recorded as 'clean'.

Neil,

I see by the switches it is watching /proc/mdstat for updates, but /proc
was likely unmounted earlier in the shutdown process, and root is now
read-only.

I've put it in the shutdown scripts and the system hangs on shutdown -
I've traced the hang to the command I put in above `mdadm --wait-clean
--scan`.

Is it possible it's waiting for a write somewhere? I'm so close to
having it working now...

Dan