The number of spinning disks in external enterprise storage continues to increase every year. Over the next five years (2008–2012), the industry will ship nearly eight times what the industry shipped over the past 11 years, according to IDC.

There is a cost beyond just acquiring these disks – the cost to power and cool them. With an aggregate worldwide electricity cost of $0.07 per kilowatt-hour last year, IDC estimates that the total amount spent on powering and cooling these drives exceeded $1 billion in 2007. It is not easy to predict the exact cost of electricity in the future, but it is easy to anticipate the direction – up.

Fortunately, there are options for companies that wish to become 'greener' in their use of enterprise storage. A number of strategies have emerged, and will continue to emerge, to help reduce the energy associated with external disk storage, including 'thin provisioning,' data deduplication, and low-power operations. End customers will likely have to decide on the trade-offs with which they are willing to live when adopting a green storage strategy.

"As companies continue to add storage capacity at an aggregate rate of over 50% per year, the number of spinning disks continues to be a larger part of the overall power and cooling costs within a datacenter," said David Reinsel, group vice president for IDC Storage and Semiconductors research. "Vendors must do more to promote and enable a well-rounded green storage strategies that includes datacenter redesign, data consolidation, and data reduction."

IDC's groundbreaking study, The Real Costs to Power and Cool All the World's External Storage, is the result of an in-depth analysis of enterprise storage worldwide and the costs to power and cool external storage arrays from 2002 to 2012. Within this study, IDC reveals the total number of spinning disks in datacenters today and estimates the real costs associated with powering and cooling these disks, as well as their commensurate carbon footprint. A number of variables were considered in this calculation, including HDD spin speeds (revolutions per minute [rpm]), interface (e.g., Fibre Channel [FC]), form factor, capacity, and workloads. In addition, IDC made allowances for power inefficiencies, controllers, fans, power supplies, and the power associated to cool the heat generated by all the power creation.