Triage: A Power-Aware Software Architecture for Tiered Microservers

Microservers are resource-rich sensor network nodes that perform complex tasks such as image processing, database query processing, localization, and target classification. While microservers can accomplish complex tasks, the required resources come at the cost of increased power consumption. To address this problem, a number of embedded platforms have employed a tiered architecture. Each tier is an independently operating subsystem containing its own memory, storage, wireless interface, and processor. Typically, such a hardware platform combines tiers with widely varying resources and power consumption characteristics. This presents a substantial opportunity to develop energyefficient software systems; however, that opportunity has not yet been fully realized. In this paper, we present the design of Triage, a software system for tiered microservers. The overarching goal of Triage is to reduce the amount of time a high-power tier must remain on by enabling a low-power tier to execute tasks on its behalf and batch work when possible. Our evaluation demonstrates that by using the low-power tier to batch file system reads and writes, we achieve a battery lifetime four times longer than a system that wakes the high-power tier for every operation. Further, using the low-power tier to execute smaller image processing tasks can increase the system lifetime by up to four times.