Consultation

Hello I would like a database (MySql) expert to advise me on a course of action - I have multiple streams of data that needs to be packed into a MySql database. The data (from each site) will arrive with ten or fifteen minute intervals. Some of this data will be processed on the website for use in simple display graphs (component on a Joomla site) that was specifically created for the purpose. The data for these graphs lies in different tables, in a database outside of the Joomla database. My problem is this: Does it pay (in terms of website performance) to have one large database for the data, or is it better to keep the bulk database separate from the database for the graphs in terms of website performance, or does it not matter? The joomla component does no processing, but only reads data from the tables within the database. I envisage to do the processing with some php script in the background as the data arrives on site.