On Thu, 29 May 2014 07:52:02 +0200 forumscollective@gmail.com wrote:

> > I doubt there is a difference between Ubuntu and Arch here.
> > 
> > The array should show "active" in "mdadm --detail" output for 200ms after the
> > last write, and then switch to 'clean'.
> > So if you are writing every 100ms, it will always say "active".
> > 
> > NeilBrown
> 
> For some reason this array has never shown Clean status, only Active.
> 
> It isn't written to other than when NFS mounted for adding new content.
> 
> Any idea what would cause constant writing - I presume from what I see that the initial array sync completed?--

Hmmm...
Do the numbers in /proc/diskstats change?

  watch -d 'grep md0 /proc/diskstats'

What is in /sys/block/md0/md/safe_mode_delay?
What if you change that to a different number (it is in seconds and can be
fractional)?

What  kernel version (uname -a)?

NeilBrown