The requirements probably change depending on where you are, but, having just finished my MSc in the UK, I can tell you what I was told supervisors are looking for in a Master's dissertation.
Some of the requirements I had have already been listed by seteropere. Basically, demonstrate you know your chosen topic very well, identify some challenges, perhaps try to tackle one.
But the main thing that supervisors here are looking for is that you have gone beyond the material in the course. They want to see that you took what you learnt throughout the taught part of the masters program and applied it to something that wasn't covered, or in a way that wasn't discussed. Alternatively, you could also choose a topic that wasn't covered at all in your course and provide an overview of it, discussing challenges, open questions, important examples (which is where dissertations that are basically just literature reviews come in, as mentioned by Legendre).
Good luck with your thesis! Unfortunately I don't know much about cloud computing, but I hope this helps anyway!