I just wanted to say I ran into this on Ubuntu 16.04 just now, and it's still not fixed.
Seems there are multiple bug id:s
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=787950#10
https://bugs.launchpad.net/debian/+source/mdadm/+bug/1550823
But this is still not fixed in Ubuntu 16.04, potentially in Debian as well.
So it might be good for everybody to know that their arrays most likely aren't being periodically checked if you upgrade to Ubuntu 16.04 currently.
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Mikael Abrahamsson email: swmike@swm.pp.se