How to install GlusterFS with a replicated high availability storage volume on Ubuntu Linux 16.04 LTSnixCraft

I want to share my web server DocumentRoot /var/www/html/ across 2 Apache web server. Both of my web servers are behind load balanced reverse proxy powered by Nginx. How do I setup and install GlusterFS ("distributed storage") which is a scalable network filesystem on Ubuntu Linux 16.04 LTS server?