Seems like after every OMV update I need to go back and add the interval in to /etc/collectd.collectd.conf
I found this page - http://info4admins.com/tips-to…disk-in-debian-or-ubuntu/ which led me to
cat /proc/sys/vm/dirty_writeback_centisecs
which by default was set to 500 (5 secs). I changed that to 90000 (15 minutes) and now my disk lights up ONCE a minute for raid sync (jbd2/md). So that got rid of the raid flush's 1-2 times per minute. Still looking to increase that.