Page 67 - How Cloud Computing Is Transforming Business and Why You Cant Afford to Be Left Behind

THE AMORPHOUS CL OUD

Research Projects Agency (DARPA), wanted a network that
would survive a nuclear attack; what it got was the birth of the
Internet. The routers on the Internet detect when a router
in the next network segment isn’t working and automatically
route around it. Likewise, when a server in a cloud data cen-
ter fails, the managing software routes the workload elsewhere

and doesn’t send that server anything more to do until it’s
fixed.
A fault-tolerant data center made from inexpensive parts
used to be an oxymoron. At one time, Tandem Computers
achieved fault tolerance, but only by running identical com-
puters side by side doing the same work, so that one could fail
without an impact on the business. Now fault tolerance is one

of the secrets behind elasticity. If adding hardware is a simple,
low-cost task, then hardware can be pulled on line as needed.
If failures occur, as they inevitably do, they can be managed
routinely and the data center will continue functioning. This
is a central principle of what Holzle and Barroso called “The
Data Center as a Computer: An Introduction to the Design of
Warehouse-Scale Machines,” their Synthesis Lecture on Com-
puter Architecture at the University of Wisconsin, Madison.
One additional example: as noted before, the large clus-

ter needs an interconnect that ties it into the other machines
in the cluster. Many have wondered how Google’s warehouse-
scale machine achieves this, and have assumed that it used the
highest-speed interconnects available to achieve the speeds
that it does. High-speed interconnects, however, are also the
most expensive method, violating the principle that the cloud

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