There are well known problems of course. The most obvious relates to guaranteeing the security of data when it is stored on computers that that a user does not own and that many others can also access. But various solutions have emerged such as encrypting data before it is sent to the cloud. For that reason, the migration to the cloud is proceeding at full speed in many places.

That may be folly. Today, Bryan Ford at Yale University in New Haven says that the full risks of this migration have yet to be properly explored. He points out that complex systems can fail in many unexpected ways and outlines various simple scenarios in which a cloud could come unstuck.

via The Hidden Risk of a Meltdown in the Cloud – Technology Review.

Now Ford imagines the scenario in which both load balancing programs operate with the same refresh period, say once a minute. When these periods coincide, the control loops start sending the load back and forth between the virtual servers in a positive feedback loop.