Oracle Database Discussions

Hi,
I'm trying to convince our systems administrator about the need for us to use Oracle Grid Infrastructure with our 11gR2 database installation. I find that I'm not really sure what the main advantages are, could you help please?
- What is the main advantage of Oracle Grid Infrastructure, what is it that will make me use it as opposed to conventional method of storage?

Any documentation recommendation would help please. I have been on the 11gR2 course and I have Oracle documentation but I am unable to see (or maybe it is lack of understanding) what is the main thing that will make us use it over an installation that uses file system storage.

thanks