Power Optimization in Disk-Based Real-Time Application Specific Systems”, UCLA, CS Dept.

ABSTRACT Introduction Magnetic disks are the de-facto standard for providing non-volatile high volume memory capacity in modern computer systems. Disks provide superior trade-off with respect to common design metric such as cost, memory capacity, latency, data input-output bandwidth and reliability in comparison with all other alternatives. Until recently, disks have been used mainly in general purpose computing systems. However, convergence of several application and technological trends resulted in the rapidly increasing importance of massive storage in application specific systems. There is rapid growth in applications such as internet-based servers (e.g. world wide web), video-on-demand, interactive television, and video conferencing, all of which have as dominating components large volume data management. At the same time technological trends indicate that key design metrics of modern and future application specific designs, such as speed, power, and weight, are dominated by massive storage elements. Most often, magnetic disk is already a bottleneck in current application specific computer and communication systems. Another equally pronounced consequence of the current application and technological trends is increasing importance of power minimization. Our main strategic objective is to give impetus for research and development of synthesis and compilation techniques for design of massive storage-based application specific systems. We have three main technical goals in this paper: 1. To establish an accurate, but computationally efficient, performance and power consumption models for disk-based systems. 2. To identify most effective ways to reduce power in disk-based application specific systems. 3. To develop a practical approach and optimization synthesis algorithms for a scheduling and assignment of disk-based real-time systems. The detailed description of the synthesis approach for optimization of disk-based application specific systems can be found in Background Material In this section we first provide an overview of power consumption sources in a disk and briefly discuss the most popular timing models of a magnetic disk. We conclude the section, by explaining the selected hardware and computational models. The detailed description of disk technology is available in Power required by a hard disk drive is consumed by its many different components. To complicate matters even further, the power requirements of each component will vary with the current operational mode of the disk. Common operational modes with different power requirements are: Start-up, Seek, Read/Write: Idle, Standby and Sleep. In each of the distinct operational modes available, a different amount of strain is placed upon each of the individual disk components, varying the amount of power consume