A total of 568 hours of downtime at 13 well-known cloud services since 2007 had an economic impact of more than $71.7 million dollars, said the International Working Group on Cloud Computing Resiliency. The average unavailability of cloud services is 7.5 hours per year, amounting to an availability rate of 99.9%, according to the group's preliminary results. "It is extremely far from the expected reliability of mission critical system (99.999%). As a comparison, the service average unavailability for electricity in a modern capital is less than 15 minutes per year," the researchers noted in their paper.
It is the first time that the group, formed in March 2012 by Telecom ParisTech and Paris 13 University, published what it calls the Availability Ranking of World Cloud Computing (ARWC). As cloud services appeal more and more to government agencies and global businesses, it becomes more important that the provided services are reliable, especially when the systems are mission critical, the researchers said. The lack of cloud reliability is not commonly known by the industry, they added. Their research is based on press reports of cloud outages at services like Twitter, Facebook, Amazon, Microsoft, Google, Yahoo and Paypal, among others.