Cisco’s newly released Global Cloud Index estimates that annual global cloud traffic will grow from 130 exabytes to 1.6 zettabytes by 2015. The kicker, though, is that only 17 percent of that 1.6 zettabytes—equivalent to 22 trillion hours of online video*—actually goes from the cloud to end users via services like video streaming or web surfing. The vast majority (76 percent) of the data that the cloud shuffles around is internal to the datacenter, and the remaining 7 percent of traffic is datacenters communicating with each other.

The report suggests that this lopsided ratio of internal to...

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