Global cloud computing traffic will grow 12-fold from now to 2015, according to a new Cisco study.

The growth represents a 66% compound annual rate, from 130 exabytes to 1.6 zettabytes, which is the equivalent of 22 trillion hours of streaming music, or 5 trillion hours of business Web conferencing with a webcam, or 1.6 trillion hours of online high-definition video streaming. Cloud is the fastest growing component of data center traffic, which itself will grow fourfold at a 33% compounded annual rate to reach 4.8 zettabytes annually by 2015, according to Cisco.

Cloud is estimated today to be 11% of data center traffic, growing to more than 33% of the total by 2015, Cisco says. Greater virtualization and improved economies of scale will be key drivers of the cloud transition; cloud data centers offer better performance, higher utilization and greater ease of management than traditional data centers, Cisco claims.

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The findings are part of Cisco's first Global Cloud Index study, developed to estimate global data center and cloud-based IP traffic growth and trends. In it, Cisco found that the majority of data center traffic comes from applications such as backup and replication, not from end-users.

By 2015, 76% of data center traffic will remain within the data center itself as workloads migrate between various virtual machines and background tasks take place. Seventeen percent of the total traffic will leave the data center to be delivered to the end user, while an additional 7% of total traffic will be generated between data centers through activities such as cloud-bursting, data replication and updates, Cisco says.

But due to the rise in video-based consumer services, data-center-to-user traffic will have some significant peaks in activity. The average amount of data center traffic per hour during peak periods is expected to rise up to 2.5 times, requiring the need to plan for additional capacity from data centers and the cloud as well as from the network, Cisco says, adding that the on-demand model of cloud is optimized for this type of variable demand.

That means, use of cloud will grow vs. traditional data centers. In 2010, 21% of workloads were processed in a cloud-based data center with 79% being handled in a traditional data center; 2014 will be the first year where the balance of workloads shifts toward the cloud, Cisco says.

At that time, 51% of total workloads will be in a cloud environment vs. 49% in the traditional IT space, Cisco says. Overall, the data center workload from 2010 - 2015 is growing almost threefold while the cloud workload from 2010 - 2015 is growing more than 7x, Cisco says.

So, to quote an old Cisco advertising campaign, "Are You Ready?" Or better yet, who is?

All regions included in the study - Asia Pacific, Middle East and Africa, Western Europe, Central and Eastern Europe, Latin America and North America - are currently ready for basic cloud-computing applications, such as social networking and Web conferencing, based on factors such as broadband ubiquity, average upload and download speeds, and average latency.

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For cloud-computing applications such as video chat and high-definition video streaming, Asia Pacific, Western Europe, Central and Eastern Europe, and North America are considered to have average network capabilities strong enough to support these services. No region, however, was assessed to be able to support "advanced" cloud applications such as high-definition video conferencing and advanced gaming. But certain countries within each region -- such as South Korea and Japan -- are currently able to do so, Cisco says.

The Cisco Global Cloud Index is generated from a modeling and analysis of various primary and secondary sources, including more than 30 terabytes of data generated each month over the past year from a variety of data centers around the world, measurements of more than 45 million broadband-speed tests, and third-party market forecasts.

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