MySQL with Glusterfs Storage vs MySQL replication with hostPath storage
The minimum for an HA setup is 3 nodes, geographically distributed.


If you put all the nodes in a single data center, you are vulnerable to a datacenter crash.  (They do happen.)
If you use Master + Slave(s), failover is not well automated.  See MHA as a possible alternative.
With Galera cluster, you can write to all nodes, thereby helping minimize downtime.  (I don't know about Glusterfs.)