You know a technology trend is all-pervasive when you see New York Times op-eds about it — and this week saw the first Times op-ed about cloud computing, by Jonathan Zittrain. I hope to address JZ’s argument another day. Today I want to talk about a more basic issue: why we’re moving toward the cloud.
(Background: “Cloud computing” refers to the trend away from services provided by software running on standalone personal computers (“clients”), toward services provided across the Net with data stored in centralized data centers (“servers”). GMail and HotMail provide email in the cloud, Flickr provides photo albums in the cloud, and so on.)
The conventional wisdom is that functions are moving from the client to the server because server-side computing resources (storage, computation, and data transfer) are falling in cost, relative to the cost of client-side resources. Basic economics says that if a product uses two inputs, and the relative costs of the inputs change, production will shift to use more of the newly-cheap input and less of the newly-expensive one — so as server-side resources get relatively cheaper, designs will start to use more server-side resources and fewer client-side resources. (In fact, both server- and client-side resources are getting cheaper, but the argument still works as long as the cost of server-side resources is falling faster, which it probably is.)
This argument seems reasonable — and smart people have repeated it — but I think it misses the most important factors driving us into the cloud.
For starters, the standard argument assume that a move into the cloud simply relocates functions from client to server — we’re consuming the same resources, just consuming them in a place where they’re cheaper. But if you dig into the details, it looks like the cloud approach may use a lot more resources.
Rather than storing data on the client, the cloud approach often replicates data, storing the data on both server and client. If I use GMail on my laptop, my messages are stored on Google’s servers and on my laptop. Beyond that, some computation is replicated on both client and server, and we mustn’t forget that it’s less resource-efficient to provide computing inside a web browser than on the raw hardware. Add all of this up, and we might easily find that a cloud approach, uses more client-side resources than a client-only approach.
Why, then, are we moving into the cloud? The key issue is the cost of management. Thus far we focused only on computing resources such as storage, computation, and data transfer; but the cost of managing all of this — making sure the right software version is installed, that data is backed up, that spam filters are updated, and so on — is a significant part of the picture. Indeed, as the cost of computing resources, on both client and server sides, continues to fall rapidly, management becomes a bigger and bigger fraction of the total cost. And so we move toward an approach that minimizes management cost, even if that approach is relatively wasteful of computing resources. The key is not that we’re moving computation from client to server, but that we’re moving management to the server, where a team of experts can manage matters for many users.
This is still a story about shifts in the relative costs of inputs. The cost of computing is getting cheaper (wherever it happens), so we’re happy to use more computing resources in order to use our relatively expensive management inputs more efficiently.
What does tell us about the future of cloud services? That question will have to wait for another day.
