How does AppZero handle application stacks?

Multiple VAAs can be combined to form an application stack.  For instance take an Apache Web server running Wordpress on a My SQL database.  You can create one VAA that has My SQL and one that has Apache server.  In this scenario, it would be typical to have a gold version of My SQL and a vanilla Web server.

You would also have a highly specialized version of the Wordpress infrastructure elements and app.  You could split that part into two VAAs – Wordpress web site and Wordpress data files.  When you run them “in context” they run as one.  The in context view is through all of these layers.  The context of all those layers are visible to the Wordpress app and it appears to be one running system. 

In the case of Wordpress, when it makes a database change, we can set it up that it is contained in/written to the Wordpress data VAA as opposed to the underlying My SQL VAA.  That keeps the Wordpress data separate from the generic MySQL database implementation.