RDBM's Open Source Or Proprietary For HA?
Recently, I was involved in setting up a 3 node MariaDB-Galera cluster; I have worked previously on SQL Server mirroring and it was interesting to contrast the two. The biggest difference in those two different methodologies is that the MariaDB-Galera cluster is a fully active, "always-on" cluster whereas SQL Server mirroring is active-passive. Of course SQL Server now supports "always-on".
The other big difference is direct/up front cost, as in licenses. As I often state the biggest cost in IT is labour and in this case the Galera cluster was no more difficult to configure than SQL Server, so labour costs were little different. With this in mind, here is a recent article from Gartner on this very subject of open source and propritary RDBM's
"By 2018, more than 70% of new in-house applications will be developed on an open-source DBMS and 50% of existing commercial relational DBMS instances will have been converted, or will be in the process of conversion.
By 2017, more than 70% of new database deployments will leverage cloud for one or more use cases."