Create a PostgreSQL appliance

PostgreSQL is a fully featured object-relational database management system. It supports a large part of the SQL standard and is designed to be extensible by users in many aspects. Some of the features are: ACID transactions, foreign keys, views, sequences, subqueries, triggers, user-defined types and functions, outer joins, multiversion concurrency control.

It makes a lot of sense to segregate a database on a separate machine / appliance.
Separating different components into different machines makes it easier to monitor load and do resource re-allocation in a VM (e.g., increase memory, add CPU, etc.)

Notes:
* the database server will have to be accessible via TCP by default
* possibly implement phpPGAdmin for easy administration
* include webmin firewall module (configure who can access the system/database)