Re: mdadm forces resync every boot

[Daniel Frey <djqfrey@gmail.com>]

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