There is an ever increasing emphasis by storage suppliers on the power efficiency of their systems. Storage vendors have been quick to respond to this in a variety of ways. The goal is to buy less storage upfront, use less of what you have already and lower the amount of additional physical spindles being added to solve performance issues. Theoretically data could be rearranged so that shelves of storage could be turned off. In our next entry we will look at how MAID storage has evolved as well as how Solid State Disk can also lead to powering off drives.”]
Source: https://www.darkreading.com/database-security/classifying-green-storage