Big Data tools and relational BI analysis tools used in different stage of data analysis

I was thinking about the relationship between traditional BI platforms and Big Data analytic tools. I think they should coexist and service for different stage of data analyzing. That is, with the Data first approach, people use Big Data analytic tools to explore data and find out right question. Then, with right and interesting question, people drill data and try to give out answers in relational database based BI platform.

I happened to watch a presentation given by Facebook. It looks they are use both Big data tools and relational DB tools for different stages of data analysis. Below is cited from the presentation and video on youtube.