Reducing Energy Consumption using a Non-Volatile storage cache

We can outperform the most powerful disk spin-down algorithm available by using a small non-volatile storage write-only cache to temporarily store hard disk write requests while a disk is spun-down. In our experiments, we use a USB thumb drive device as our non-volatile storage cache. By redirecting writes to a flash memory while a disk is spun-down we avoid costly hard disk cycle start-stop operations, thus increasing hard disk reliability and reducing energy consumption. We also show that such a storage cache is necessary to provide feasible performance from a disk spin-down algorithm in a general purpose operating environment. The problem arises from typical general purpose operating system applications generating periodic disk activity while a system is not in use. By using small, cheap, and nonvolatile flash memory we can improve the energy savings of a highly adaptive machine learning disk spin-down algorithm by 36%, and the 15 and 45 second fixed-timeout algorithm by 57% and 46%, respectively. We can also reduce the relative fraction of hard disk ”contact start-stop cycles” by 80% for the DSA algorithm, and with the 15 and 45 second fixed-timeout algorithm 79% and 73%, respectively.