The glusterfs-server upstart conf would start before the brick was mounted. I added this ugly hack to get it working. I ripped the pre-start script from mysql and decided to leave the sanity checks in place, just because.

glusterfs-server.conf

author "Louis Zuckerman <me@louiszuckerman.com>"
description "GlusterFS Management Daemon"

start on runlevel [2345]
stop on runlevel [016]

pre-start script
    #Sanity checks
    [ -r /etc/glusterfs/glusterd.vol ]
    [ -d /var/lib/glusterd ] || install -m 755 -o root -g root -d /var/lib/glusterd
    /bin/sleep 10
end script

expect fork

exec /usr/sbin/glusterd -p /var/run/glusterd.pid

Hacked by me, btw, not Louis.