https://help.ubuntu.com/community/HighlyAvailableNFS
http://www.linux4beginners.info/linux-how-to/how-to-setup-redundant-nfs-servers-heartbeat-drbd-nfs-centosredhatubuntudebian/
gs2:
https://wiki.ubuntu.com/ClusterStack/Precise
ubuntu(当前主要参考):
https://wido.me/sunteya/deploy-high-availability-database-server-on-ubuntu
drbd:
https://github.com/chenzhiwei/linux/tree/master/drbd