Cloud Computing

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HE GREEk MYTHS tell of creatures plucked from the surface of the Earth and enshrined as constellations in the night sky. Something similar is happening today in the world of computing. Data and programs are being swept up from desktop PCs and corporate server rooms and installed in “the compute cloud.” Whether it’s called cloud computing or on-demand computing, software as a service, or the Internet as platform, the common element is a shift in the geography of computation. When you create a spreadsheet with the Google Docs service, major components of the software reside on unseen computers, whereabouts unknown, possibly scattered across continents. The shift from locally installed programs to cloud computing is just getting under way in earnest. Shrink-wrap software still dominates the market and is not about to disappear, but the focus of innovation indeed seems to be ascending into the clouds. Some substantial fraction of computing activity is migrating away from the desktop and the corporate server room. The change will affect all levels of the computational ecosystem, from casual user to software developer, IT manager, even hardware manufacturer. PHOTOGRA PH BY RICHA RD M ORGENST EIN

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Technology | DOI: 10.1145/1364782.1364786

Brian Hayes
When personal computers arrived in the 1980s, part of their appeal was the promise of “liberating” programs and data from the central computing center. (Ted Nelson, the prophet of hypertext, published a book titled Computer Lib/Dream Machines in 1974.) Individuals were free to control their own computing environment, choosing software to suit their needs and customizing systems to their tastes. But PCs in isolation had an obvious weakness: In many cases the sneakernet was the primary means of collaboration and sharing. The client-server model introduced in the 1980s offered a central repository for shared data while personal computers and workstations replaced terminals, allowing individuals to run programs locally. In the current trend, the locus of

cloud computing
As software migrates from local PCs to distant Internet servers, users and developers alike go along for the ride. In a sense, what we’re seeing now is the second coming of cloud computing. Almost 50 years ago a similar transformation came with the creation of service bureaus and time-sharing systems that provided access to computing machinery for users who lacked a mainframe in a glass-walled room down the hall. A typical time-sharing service had a hub-and-spoke configuration. Individual users at terminals communicated over telephone lines with a central site where all the computing was done.

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computation is shifting again, with functions migrating outward to distant data centers reached through the Internet. The new regime is not quite a return to the hub-and-spoke topology of time-sharing systems, if only because there is no hub. A client computer on the Internet can communicate with many servers at the same time, some of which may also be exchanging information among themselves. However, even if we are not returning to the architecture of time-sharing systems, the sudden stylishness of the cloud paradigm marks the reversal of a long-standing trend. Where end users and corporate IT managers once squabbled over possession of computing resources, both sides are now willing to surrender a large measure of control to third-party service providers. What brought about this change in attitude? For the individual, total control comes at a price. Software must be installed and configured, then updated with each new release. The computational infrastructure of operating systems and low-level utilities must be maintained. Every update to the operating system sets off a cascade of subsequent revisions to other programs. Outsourcing computation to an Internet service eliminates nearly all these concerns. Cloud computing...
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