Software-directed data access scheduling for reducing disk energy consumption

Most existing research in disk power management has focused on exploiting idle periods of disks. Both hardware power-saving mechanisms (such as spin-down disks and multi-speed disks) and complementary software strategies (such as code and data layout transformations to increase the length of idle periods) have been explored. However, while hardware power-saving mechanisms cannot handle short idle periods of high-performance parallel applications, prior code/data reorganization strategies typically require extensive code modifications. In this paper, we propose and evaluate a compiler-directed data access (I/O call) scheduling framework for saving disk energy, which groups as many data requests as possible in a shorter period, thus creating longer disk idle periods for improving the effectiveness of hardware power-saving mechanisms. As compared to prior software based efforts, it requires no code or data restructuring. We evaluate our approach using six application programs in a cluster-based simulation environment. The experimental results show that it improves the effectiveness of both spin-down disks and multispeed disks with doubled power savings on average.