Abstract

In this paper we examine the impact of using flash memory as a second-level file system buffer cache to reduce power consumption and file access latency on a mobile computer. We use trace-driven simulation to evaluate the impact of what we call a FlashCache. We relate the power consumption and access latency of the storage sub-system to the characteristics of the FlashCache: its size, the unit of erasure, and access costs. We find that a FlashCache can reduce the power consumption of the storage subsystem by 20-40% and improve overall response time by 30-70% when combined with an aggressive disk management policy. When combined with a more conservative policy, power is reduced from 40-70% while overall response time is improved 20-60%. We also find that durability is not a problem; a 4 MB FlashCache will last 33 years. 1 Introduction The storage subsystem on a mobile computer, usually consisting of DRAM and magnetic disk, is an important consumer of battery power. Table 1 lists the ...

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