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

quoted

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