Some Ubuntu users have reported errors mounting GlusterFS volumes at boot time due to the order that the Upstart system init daemon starts services. Gluster community member Semiosis posted a solution:
On Ubuntu, if you add a glusterfs volume to the fstab on a server, using localhost as the server address, you’ll find that the volume does not get mounted at boot time. This is because the fstab mounts are executed before the glusterd service has been started during the boot process.
Ubuntu uses the upstart system init daemon, and it uses a special daemon called mountall to execute the fstab mounts. Because of this, the only way to have the glusterd service available when the fstab mounts are executed is to “upstartify” glusterd by converting the glusterd init script to an upstart job.