[[abstract]]Previous studies proposed energy-efficient solutions, such as multispeed disks and disk spin-down methods, to conserve power in their respective storage systems. However, in most cases, the authors did not analyze the reliability of their solutions. According to research conducted by Google and the IDEMA standard, frequently setting the disk status to standby mode will increase the disk’s Annual Failure Rate and reduce its lifespan. To resolve the issue, we propose an evaluation function called E3SaRC (Economic Evaluation of Energy Saving with Reliability Constraint), which considers the cost of hardware failure when applying energy-saving schemes. We also present an adaptive write cache mechanism called CacheRAID. The mechanism...