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Imagine you want to build a software-based[br]company, providing a service on the web.

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A few years ago, it used to be that you[br]needed to do two things:

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develop the software and buy[br]expensive hardware to run it on.

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That's not true anymore.

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Nowadays, you still have to develop the[br]software, of course,

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but you don't need to buy the hardware.

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You can rent it, and in ways that are[br]extremely flexible and match your needs.

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This is what's called cloud computing.

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So, what's a cloud?

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It's an abstraction of a computer or many[br]computers.

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Hmm, that doesn't really help,

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so, let's start at the beginning.

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What's a computer?

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Essentially, it has two components that are[br]important:

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Number one is memory, like a hard drive.

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Number two is a processing unit, which[br]helps derive new results from old ones.

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That's the unit that does all the[br]computation, the brain --

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the brain if you want.

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This used to only come packaged as a box,[br]with the brain and the memory together.

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For instance, think of your laptop or your[br]desktop.

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So let's look at a typical example, [br]such as the Coursera start-up,

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and its options for growing.

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At the beginning you just have a few students [br]using the platform,

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which runs on one server.

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Then that central processing unit and storage unit [br]-- so the brain and the memory --

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will do everything, switching between[br]serving videos to different students,

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serving pages, computing grades, searching[br]posts in the forums, etcetera.

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This would work well, [br]but as soon as Coursera is successful,

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it doesn't work anymore.

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You have to buy new servers, keep up with[br]demand, and also keep everything balanced.

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You have to make sure that you have [br]the right number of these machines,

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at the right place.

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And it's going to be expensive if you[br]under-use some parts of them.

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Now with cloud computing, this is[br]essentially not a problem anymore.

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You get very flexible computing units [br]and very flexible storage units.

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They're flexible simultaneously in[br]geographical location and in size.

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So you can ramp each, [br]depending on real needs.

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For instance, in the evening, Coursera will[br]probably see higher loads

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from most of the students doing their homework [br]and it can adapt easily to that.

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Who provides those cloud computing services?

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Well, more and more companies do that,

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but the most famous is probably [br]Amazon Web Services.

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This is a part of Amazon that was created

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to answer their own needs with their[br]e-commerce website

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that would see huge demands around[br]Christmas and so on.

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Writing software that uses cloud computing[br]is not so hard,

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but it's very hard to rewrite software [br]that was written

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before these ideas took hold.

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Older learning management systems, that[br]did not explore those ideas,

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even if they were really good [br]at the services provided,

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will probably need to be rewritten,

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in order to scale to millions of students.

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Not everything is perfect [br]with cloud computing, though.

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Since the data is heavily distributed[br]around the world,

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a whole lot of new problems can come,[br]relating to data privacy, for instance.

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[CC BY-SA[br]Paul-Olivier Dehaye]