Power consumption is a major problem for data centers of all sizes which impacts the density of servers and the total cost of ownership. This is causing changes in data center configuration and management. Some components already support some power management features, for example server CPUs support dynamic clock and voltage scaling that enables power requirements to be reduced significantly during idle periods. Storage subsystems do not have power management and are consume a significant amount of power in the data center. Modern enterprise grade disks require approximately 10W when idle. As storage requirements generally increase in data centers, the number of disks in data centers is increasing proportionally.
Current Status
Based on 1-week long traces of core servers in our data center, we have found that there are significant periods of idle time during which disks can be spun down, and even longer “write-only” periods during which all I/O operations are writes. Based on this we have developed a technique called “write off-loading” which allows disks to stay spun down during these write-only periods, by temporarily off-loading the write requests to other volumes in the data center. Our results show that this provides power savings of 45—60%. This work will presented at the Usenix FAST conference in February 2008.
- D. Narayanan, A. Donnelly, A. Rowstron. “Write Off-Loading: Practical Power Management for Enterprise Storage” in 6th USENIX Conference on File and Storage Technologies (FAST ’08).
