The challenge is managing these systems to make sure that data is stored on them in such a way that the amount of off or idle time is maximized to realize that power savings. If data is stored to the drive and then 15 minutes later is accessed again, the drive has to spin back up and serve out the data. The problem is that this type of use case may actually increase power consumption. As a result, how you group and place data on these systems becomes critical. Some systems automatically take care of data placement, while others require manual planning on the part of the administrator.
Another option is the use of disk backup or archive systems like those offered by Permabit or Tarmin Technologies. While these systems don't really offer any power management features like drive spin down, they are designed to offer very dense capacity with data optimization like deduplication at very aggressive price points. This, then, requires some justification from a green perspective. If you can free up 2 TB's of primary Fibre storage that is on about seven 300-GB drives and instead store that on two 1-TB drives, even if the drives use the same power, there are less of them and essentially this is more green.
The decision is yours; do you go with the purest definition of green storage, spun down or powered off drives, or do you go with the low-cost, high-capacity disk archive model? Each have their benefits and a total calculation must be made that includes energy savings as well as purchase costs against the cost to power and cool more storage.
In our next entry we will look at green options for primary storage.
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George Crump is founder of Storage Switzerland, an analyst firm focused on the virtualization and storage marketplaces. It provides strategic consulting and analysis to storage users, suppliers, and integrators. An industry veteran of more than 25 years, Crump has held engineering and sales positions at various IT industry manufacturers and integrators. Prior to Storage Switzerland, he was CTO at one of the nation's largest integrators.