Comment 12 for bug 1320402

I also experienced the same problem with a IMSM RAID 1. I believe that the problem is essentially identical to the gentoo problem which was noted earlier. I put in the following workaround which seems to work (on a clean install of Ubuntu 14.04.1 with mdadm version 3.2.5). At least, I have not seen a resync on boot since putting this in this fix.

1. Edit /etc/init.d/sendsigs (to prevent mdmon from being killed on shutdown):
 OMITPIDS=`pidof mdmon | sed -e 's/ /,/g' -e 's/./-o \0'`

2. Edit /etc/init.d/umountroot (to force the system to wait for the RAID to be clean before shutdown):

##########################
#FIRST: Add the following function:
check_raid() {
 log_action_begin_msg “Checking RAIDs ”
 if mdadm --wait-clean --scan ; then
  log_action_end_msg 0
 else
  log_action_end_msg 1
 fi
}

#SECOND: change the call to do_stop:
#stop)
# do_stop
# ;;

stop)
 check_raid
 do_stop
 check_raid
 ;;
##########################

It isn't clear that check_raid has to be called both before and after do_stop (probably after will work fine, but I didn't test it).