MySQL with NFS storage

I use MySQL database with replication in three servers but my problem is the storage. For a small application has no problem, because when I need more power I create more servers and replicate all data, but now I need working with 1TB of data.

For a solution I created a NFS storage, but the MySQL does not allow two or more servers read the same data. I already working with NFS storage with my Apache servers that I can be scale up for 2 or 100 servers and read the same data, but I need know how do this with MySQL Server.

How companies like Parse, Google and Facebook works with large databases?

Sorry about my english.

​Thanks.

Is there some reason that you don’t share the same database between all 3 servers? You just need to enable remote access to the database / set up the relevant accounts / firewall everything…