How many database instances are too much with the ezcomponents database component?

I want to connect to about 9 databases and create an instance for everyone of them to aggregate my results in the queries.

I am writing a metrics dashboard for my company that need to track results and performance over about 9 different databases with about 15mil+ records in each. Now the technical part is not hard. I know how to code it but I want to find out whats the best approach.

Theres option 1 : Create one database instance and do a UNION on all my select queries. (Note: All databases are on one box)

Option 2 : Create a开发者_运维问答n instance for every database and separately query each one and aggregate the results.

This is more of a high level question if that helps.

Thanks!

It seems like the best way to connect to 9 different databases is not by an actual connection but creating an API that feeds the data to you instead you having to pull the data all the time resulting in EXTREMELY slow data population and aggregation.

Its an amazing solution to a complex question. Create a xml feed that feeds the data to you as you need it.