One of the things that most folks don't' know about Google, they build their own computers… continuously. That is a necessity when you store as much data as they do.
Of course all of that data also requires not only computers, but a place to house them. Google has several very large and very secure data centers in the U. S. and a few spread around the world as well. It's pretty amazing when you really get a handle on it.
Google stores all of their search info, youtube videos, and tons of other Google things. However, they also store lots of Gmail for customers, lots of music, calendars, and lots of data now that they are selling space on Google Drive.
If you're interested in what they do & how they do it, there is a great article on Foxnews.com
If you'd like to just head on over to Google to read and see what they're willing to tell you about all of this, they have a great website about their data centers. Enjoy!!!