That is going to be hard to achieve.

To know how to store the data, you need to know how you will query it.

If you know how you will query it, you can say devise a way to store it in Cassandra.. which will scale up to PB.

If you just throw in a PB of data, I am not aware of ANY system that is going to let you drop ad-hoc queries at the data and get fast answers. You effectively need to load most / much of the data off disk to process it.

If you only want to store it and not query it yet.. store it off on flatfile. When you decide how you will query it, load it from the flatfile and switch writes to your new system.