The most difficult aspect of cloud computing, really most computing, is the data layer. It is common for data to be a single point of failure. The reason for this is simple and lies in the very nature of data itself. To understand, take a deeper look at how data in a computing environment actually functions. Imagine a classroom full of students writing a paper. Now imagine that same class room, all students writing a paper, but all the same paper and all on the same physical sheet of paper.

Who writes what? When? What if one student is writing a sentence in the middle right when another student starts, too? Now, flash back to our scale talk and imagine we need to scale out. Think several classrooms, all with students. But instead of every classroom having its own sheet of paper, they all have to share the one sheet of paper that was created in that first classroom