Non-volatile storage is an important element for many low-power wearable sensor platforms for data aggregation, audit logs, and to enable offline analytics and debugging. NAND flash is an increasingly appealing choice due to its low cost, low power consumption, and small footprint; but it requires high software complexity and overhead to use effectively in such resource-constrained environments. Many wearable processing systems have limited program memory and RAM, on the order of kilobytes, however current NAND flash file systems require 10s of kilobytes of code and RAM to provide rudimentary logging facilities to SD cards or flash memories. By constraining access patterns to practical cases for logging and optimizing operations around the timing needs of real-time systems, we can do better. This paper presents the design and evaluation of a NAND flash logging file system, available freely under a permissive license, in only a few kilobytes of ROM and a few hundred bytes of RAM.
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