A Docked-Aware Storage Architecture for Mobile Computing

摘要

We explore how the power-abundant docked state of mobile devices can be exploited to reduce power consumption during mobile operation and expand the capabilities of portable devices. We propose a storage hierarchy,which includes a hard disk,a large low-power cache,and a docked-aware file system that lowers the average power cost of file access from the disk while retaining the storage capacity of the disk.We investigate how hoarding files in low-power memory during a power-abundant docked state can drastically reduce the power consumption of the hard disk during mobile operation.Using traced-based simulation, we determine the effects on battery run-time of adding the storage architecture to a modern palmtop device—effectively adding mass storage capability to the device.We experiment in the palmtop environment because palmtops are frequently and easily docked, and epitomize the battery and power constraints that face compact,portable devices.Our trace-based simulation shows that up to 86%of power used by the storage subsystem can be recovered using simple hoarding algorithms that cache data during the docked state.This power savings translates into simulated run-times 86%–97%as long as the run-time of a diskless palmtop.